Selective conversion of syngas to C_4+ long-chain alcohols

Domain: biology
Published: 2026-03-23
Editorial outcome: major_revision

Abstract
The selective conversion of syngas to C long-chain alcohols holds significant
4+
industrial and scientific interest, but challenges in product selectivity and process
efficiency remain. Here, we report a precisely catalytic strategy for C alcohol
4+
synthesis with a selectivity of 80% at 17% CO conversion. The reaction channel
involves: (i) the development Cs O-Co C-Co catalysts, capable of catalyzing CO
2 2
hydrogenation to long-chain oxygenates/olefins; and (ii) complete conversion to C
4+
alcohols is subsequently achieved on the single-Rh-site and Cu-ZrO interfaces by
2
integrated cooperative catalysis. A comprehensive catalyst design and compatibility
assessment of each catalytic module ensures optimSal combinations, meanwhile
effectively eliminates costly separation steps, and reduces CO selectivity down to 1%.
2
The developed process achieves ultra-high caPrbon-efficiency (>95%) and improves
oxygen-efficiency, effectively overcominNg the key limitations of current syngas
conversion technologies and thus representing a competitive and sustainable solution
for producing high-value long-chain alcohols with a minimal carbon footprint.

Introduction
C long-chain alcohols are critical chemicals with diverse applications across the food,
4+
textile, pharmaceutical, and energy sectors1,2. These alcohols serve as crucial raw
materials for a variety of fine chemicals, with specific chain lengths determining their
purposes. For instance, butanol, a key precursor in plastics (e.g., butyl acrylate and butyl
acetate) and gasoline additive, The global markets for n-butanol are projected to grow
at a compound annual growth rates (CAGR) of 6.3% during 2021-20323,4, reflecting
their economic significance. Beyond these, C -C alcohols and C -C fatty alcohols
5 9 10 20
are essential in manufacturing plasticizers, surfactants, and detergents, with global
market values projected at 8.14 and 14.98 billion USD, rSespectively5,6.

Current industrial production techniques for C alcohols, which mainly include
4+
carbonylation (OXO-synthesis) and Ziegler pProcess, face significant limitations in
terms of scalability, complexity and sustaNinability. The carbonyl synthesis process is
complicated, and the separation and recovery of the catalyst from product are difficult,
hindering its large-scale applica
tion. For the Ziegler process, ethylene oligomerization
relies on highly reactive triethyl aluminum, which restricts the production of odd-chain
primary alcohols7,8. As T global demand for C alcohols grows, alternative synthetic
4+
routes are urgently needed. Syngas-based synthesis offers a more sustainable alternative,
as it enables the utilization of diverse feedstocks such as natural gas, biomass, or even
CO . Moreover, syngas-to-C alcohols can more reasonably and efficiently transform
2 4+
oxygen-atoms from CO into organic products, which reduces CO emissions or waste
2
H O as by-products. Aldol condensation (i.e., upgrading ethanol to long-chain alcohols)
2
is an attractive route9,10, considering the industrial maturity of ethanol synthesis from
syngas-derived methanol, either via direct homogeneous carbonylation to oxygenates
or heterogeneous dimethyl oxalate (DMO) synthesis followed by subsequently
hydrogenation (Fig. S1). Despite its promise, technological immaturity and systemic
complexity prevent its industrial implementation.

Direct synthesis of higher alcohol (HA) from syngas using single catalyst is
conceptually attractive but faces serious challenges, particularly in product
selectivity11,12. The reaction network involves complex steps, including CO and H
2
adsorption, H dissociation, CO dissociation and non-dissociation activation, C-C
2
coupling between various intermediates, and product desorption13, often resulting in
undesirable by-products, including alkanes, alkenes, and CO 8. As demonstrated by
2
Wasim et al., precise control over CO activation and C-C coupling is crucial for the
selective synthesis of long-chain alcohols14, which requires rational design of
multifunctional catalysts to steer the reaction toward desired products. Despite
advances in bi- or multi-component catalysts (MoS 15, Cu-Co16-19, Cu-Fe20, Co-Fe21,
2
Co-Mn22,23, Cs-Cu-Zn24), selectivity for C alcohols remains low (ca. 20%, Fig. S1 and
4+
Table S5). Tandem catalysis approaches have achieved improved results, with notable
results including CoMn|CuZnAlZr (46% oxygenates seleSctivity)25, CuCoAl|t-ZrO (33%
2
C OH selectivity)26, CuCoAl|ZnO/ZrO (34% C OH selectivity)27,
2+ 2 2+
ZnCrAlO
x
|KNiMoS-MMO-5 (60% total alcohoPl selectivity)28, CoMn/MAC(P)|Rh/3v-
PPh
3
@POPs (60.8% total oxygenates selNectivity)29 and NaPr-CoRu/AomM|Co
2
CO
8
+
PCy (54% total alcohol)30. These novel catalytic processes have stimulated a new pulse
3
in the integrated syngas conversion chemistry, but most efforts are focused on C
2+
alcohols rather than C products. In addition to the moderate selectivity of C alcohols
4+ 4+
(30%), the process is hampered by the complex separation and distillation steps and the
limited availability of olefins. In China, a syngas-to-C alcohols process has been
4+
industrialized31, utilizing by-product olefins from Fe-based Fischer-Tropsch synthesis
(FTS) followed by hydroformylation and hydrogenation using aqueous-organic two-
phase homogeneous hydroformylation catalysis. Nonetheless, additives are
indispensable in order to enhance the solubility of C olefins in an aqueous phase,
4+
where the hydroformylation reaction was carried out, causing additional difficulties in
catalyst-product separation.

Herein, we firstly report a precisely designed integrated catalytic system for selective
conversion of syngas-to-C
4+
alcohols (Fig. S1). Appropriate design of Cs
2
O-Co
2
C-Co
key catalysts for selectively catalyzing syngas to long-chain oxygenates/olefins,
and
then the complete transformation of the cascaded hydroformylation and hydrogenation
to produce C alcohols was deeply explored. Key challenges, including achieving high
4+
selectivity toward oxygenates/olefins and ensuring compatibility among different
catalytic modules, were thoroughly studied through rational catalyst design and
comprehensive process optimization. Density functional theory (DFT) calculations
elucidated the high selectivity toward C alcohols/C olefins of a novel syngas-to-
4+ 3+
oxygenates/olefins catalyst, while compatibility assessments of integrated catalytic
modules for target products (syngas-to-oxygenates/olefins plus olefins
hydroformylation, syngas-to-oxygenates/olefins plus hydrogenation of oxygenates and
olefins, and syngas-to-oxygenates/olefins plus olefins hydroformylation plus
hydrogenation of oxygenates and olefins). Our optimized system combines Cs O-
2
Co C-Co catalysts for the highly selective syngas-to-oxygenates/olefins conversion in
2
the first reactor, the single-Rh-site catalyst for olefinSs hydroformylation and the
CuZrO /SiO catalyst for aldehydes hydrogenations in the second reactor. This
2 2
integrated approach achieved an unprecedentedP 87% total alcohol selectivity, including
80% C alcohols and 50% C alcohols,
4+ 6+
respectively, establishing a promising route
for sustainable long-chain alcohol production.

Results
Selective conversion of syngas to oxygenates/olefins

Syngas-to-oxygenates/olefins is the key step to produce C long-chain alcohols, as it
4+
not only directly determines CO conversion and product distribution, but also the
composition of the intermediates will strongly influence the catalytic performances in
subsequent hydroformylation and hydrogenation. Therefore, it is crucial to identify
appropriate catalysts for the selective conversion of syngas into oxygenates/olefins at
this stage. Carbon-supported cobalt (Co/C) was selected as the benchmark system for
its demonstrated high performance in higher alcohol synthesis, and a series of modified
analogues with different metal promoters (Mn, Cr, Ni, Ca, Ba, and Cs) was explored
(Fig. 1a and Table S1-2). When 0.5 wt.% Mn was doped in Co/C, the selectivity of C
4+
oxygenates/C olefins was markedly increased from 37% to 50% without
3+
compromising CO conversion (Fig. 1b) and Mn was assumed to promote the C-C
coupling and chain growth process32, reducing methane selectivity from 22.0% to 10.2%
(Table S1-S2 and Fig. S2). The CoMn/C with the fixed compositions was then chosen
for further optimization with a second promoter. While the additions of Cr or Ni
improved CO conversion but inhibited the formations of oxygenates/olefins, Ca and Ba
additives promoted CH formation, and great promotional effect was observed with the
4
addition of Cs (Fig. 1a). The regulation of different metal additives has little effect on
CO
2
selectivity (all less than 5%, Fig. S2). In particular, Co
0.5
Mn
0.1
Cs/C exhibited
relatively low alkanes/olefins ratios (0.7-0.9) and the highest total selectivity of
oxygenates/olefins, with the total selectivity of C oxygenates/C olefins reaching 73%
4+ 3+
(Table S1-2). Anderson-Schulz-Flory (ASF) plots have been constructed and are
compiled in Fig. S3a-d. Accordingly, a linear ASF behavior with chain lengthening
probability  = 0.65 is obtained, and as the pressure increased to 8 MPa, α increased to
0.72. Control experiments showed that additions of indSividual Mn or Cs could also
improve the total selectivity of oxygenates/olefins and reduce CH
4
selectivity, with α
values of 0.67 and 0.66, respectively, but bothP led to decreased activity (Table S1).
Under the same reaction conditions, the CNO conversion on Co Mn Cs/C (29%) was
0.5 0.1
higher than those on Co Mn/C (20%) and Co Cs/C (11%, Fig. 1b and Table S1).
0.5 0.1
The
above results strongly point to the synergy between Mn/Cs additives and the active Co
species in steering the formation of desirable products.

To understand the promotional effect of Mn and Cs co-addition, key catalysts were
characterized by multiple techniques. Powder X-ray diffraction (PXRD) patterns
revealed the typical diffraction lines corresponding to face-centered cubic (fcc) Co on
Co Mn/C, Co Cs/C, and Co Mn Cs/C (Fig. S4). The noticeable peaks at 41.3°,
0.5 0.1 0.5 0.1
42.5° and 45.7° 2 corresponding to Co C was more evidenced on Co Mn Cs/C.
2 0.5 0.1
This
result was corroborated by deconvolution of the Co 2p X-ray photoelectron spectra
(XPS) for Co Mn Cs/C, the Co 2p binding energy peaks at 780.9 and 778.3 eV
0.5 0.1 3/2
were assigned to Co2+ and Co0 species, respectively (Fig. 1c). These observations
strongly suggested the co-existence of both Co0 and in situ formed Co C on the catalyst
2
surface, which was further confirmed by detailed electron microscopic observations.
Scanning transmission electron microscopy (STEM) coupled with elemental color
mapping image of the spent CoMnCs/C catalyst unambiguously pointed to the surface
enriching of carbon species around Co nanoparticles (Fig. S5). This was further
supported by line-scanning of an individual nanoparticle, showing relatively even
distributions of Cs and Mn across the nanoparticles but much higher C signal at the
periphery (Fig. 1d). As carburization gradually accumulated, Co particles and the
carbon layer underwent further reaction under reaction conditions and were gradually
and partially converted into Co C. To validate this hypothesis, HRTEM image of the
2
spent catalyst was acquired (Fig. 1e). Lattice fringe analysis revealed the structure of
fcc-Co(111) in an individual particle decorated by small Co C ensembles (Fig. 1e).
2
Noted that Co C was present as small patches on the Co surface, forming Co C-Co
2 2
interphases, but did not fully cover the latter. To understand the individual roles of Mn
and Cs on the catalyst structure, the STEM with line-scanning images of Co/C, CoMn/C,
and CoCs/C catalysts, together with their corresponSding HRTEM images, were
acquired (Fig. S6). These results showed that the addition of Mn alone also promoted
the clear carbon enrichment on Co particles and in situ formation of Co C-Co structure
2
during FTS reaction, which were not obseNrved on Co/C and CoCs/C. Considering that
Cs was mainly enriched on Co nanoparticles for the best-performing CoMnCs/C
catalyst (potentially existing as Cs+ species due to the nature of electronic promoter,
also supported by DFT calculations in Table S3), the Cs O-Co C-Co model was
2 2
constructed for further simulation. In addition, statistic counting of TEM images
revealed that the particle size of CoMnCs/C was significantly reduced as compared with
the other two individually promoted ones (D = 6.9 vs. 8.0 and 8.6 nm, Fig. S7), thus the
increased dispersion might thereby increase the exposed Co and Co C active sites and
2
improve the catalytic activity. The interfacial sites of Co C and Co nanoparticles,
2
denoted hereafter as Co
2
C-Co, are crucial for the preferential formation of alcohols33 34,
and the addition of Cs can further enhance alcohol formation. Based on these
observations and the catalyst characterization data, a new catalyst model of Cs O-Co C-
2 2
Co, plus Co(111) and Co C-Co, was constructed to further elucidate their effects on the
2
syngas-to-olefins/oxygenates activity and product distribution through DFT
simulations (Fig. S8, Table S3). To explain the different product distributions, three key
fundamental steps including the formation of alkanes, olefins, and oxygenates from
alkylidyne species (C H CH C*), the presumed key reaction intermediates, were
3 7 2
simulated (Figs. 1f, S8-S11, and Table S3). For Co(111), the energy barrier for the
formation of alkanes from C H * is much lower than those for olefins and oxygenates
5 9
(1.05 vs. 1.83, 1.37 eV), explaining the high propensity of deep hydrogenation on pure
metallic cobalt. In contrast, the C
5
H
9
* intermediates are more prone to forming
C H CHCH * or undergoing CO insertion instead of hydrogenation to alkanes on Co C-
3 7 2 2
Co and Cs
2
O-Co
2
C-Co, suggesting that Co
2
C-Co interphase can generally enhance the
formations of olefins and oxygenates. To further reveal the promotional role of Cs, the
energy barrier differences between C H * hydrogenation to alkanes and olefins, CO
5 9
insertion were calculated and used as a selectivity indicator. A larger difference was
observed on Cs O-Co C-Co than on Co C-Co (0.44 vs. 0.06 eV), explaining the
2 2 2
improved selectivity towards oxygenates/olefins on the Sformer. To further understand
the promotional effects of Cs addition on syngas-to-oxygenates/olefins activity, we
calculated the projected density of states (PDOSP) for the different models (Fig. S12).
It
was found that the 3d occupied and unoccNupied electronic states of Co in Co(111) are
significantly localized near the Fermi level. This indicated that the 3d electrons of Co
are not easily engaged in strong interactions with the 2p orbital electrons of the adsorbed
CO, due to a mismatch in their energy levels. In comparison to the Co C-Co model, the
2
incorporation of Cs markedly broadens the distribution of Co's 3d orbitals, particularly
promoting the extension of the 3d orbitals toward lower energy levels. This effectively
enhances the interaction between the C 2p and Co 3d orbitals, facilitating CO activation
as also supported by the Bader charge analysis (Fig. 1f). Therefore, the combined
experimental and theoretical studies provide a molecular-level understanding of the
roles of Cs and Mn in regulating the electronic properties of the active sites in Co-based
catalysts, achieving directional modulation over the syngas-to-oxygenates/olefins
reaction steps through precise engineering of the active Cs O-Co C-Co architectures
2 2
that efficiently suppress excessive hydrogenation and facilitates direct CO insertion,
thus enhancing the selectivity of oxygenates/olefins.

Interplay between different catalytic modules and compatibility.

Since substantial amounts of olefins (25-40%) and aldehydes (10-20%) were produced
during the syngas-to-oxygenates/olefins (Table S1), it is advantageous to convert them
into C alcohols by employing additional heterogeneous hydroformylation and
4+
hydrogenation steps. To this end, the compatibility of the combined process between
syngas-to-oxygenates/olefins and olefins hydroformylation/aldehydes hydrogenation
was investigated. Two porous organic polymers (POPs)-supported single-Rh-site
catalysts (Rh /3v-POPs-PPh and Rh /POPs-BP&PPh , PXRD, ac-HAADF-STEM,
1 3 1 3
Figs. S13-S14) with strong coordination bonds between Rh and exposed P embedded
into the framework of POPs (XPS, Fig. S15) were selected as the heterogeneous
hydroformylation candidates owing to their documented hydroformylation
performance35-36. The performance of the catalysts in syngas-to-oxygenates/olefins plus
hydroformylation of olefins showed comparable CSO conversion and product
distribution (Fig. 2a). Both alcohols and aldehydes were the major products while
selectivity of olefins was below 1%, suggesting Psuccessful transformation of the formed
olefins into aldehydes through hydrofoNrmylation chemistry. In addition, different
hydroformylation catalysts can effectively regulate the normal and isomeric (n/i) ratio
of alcohols and aldehydes (Table S4).

Selective hydrogenation process is particularly crucial for the catalysis system of
syngas-to-oxygenates/olefins plus hydrogenation of oxygenates and olefins, as the
presence of CO and the water generated from syngas-to-oxygenates/olefins could
significantly impact hydrogenation performance37. In addition to the poisoning effect
of CO on hydrogenation catalysts, other side reactions could occur including
generations of CH and methanol, and water-gas shift reaction38,39. To identify potential
4
candidates for the selective hydrogenation of aldehydes, a broad screening of Cu-, Ru-,
Pd-, and Pt-based hydrogenation catalysts was performed (Fig. 2a). Several trends
emerged among the different catalyst families. Pd- and Ru-based catalysts displayed
lower activity in the hydrogenation of aldehydes compared to previous studies40,41,
likely due to CO poisoning. Similarly, the pristine Pt/TiO
2
showed minimal activity,
while the Sn-modified Pt/TiO demonstrated good performance in the selective
2
hydrogenation of aldehydes to alcohols. The excellent performance could be originated
from the electronic effect of Sn, leading to markedly increased electron density around
Pt species (Fig. S16, XPS)42. Lastly, Cu-based catalysts displayed high hydrogenation
activity in the CO-rich feeds, although product selectivity varied markedly. Olefin
hydrogenation was significantly enhanced, accompanied with boosted formation of
alkanes and CO on Cu/SiO , pointing to vigorous hydrogenations of both aldehydes
2 2
and olefins. In stark contrast, CuZrO /SiO exhibited excellent selective hydrogenation
2 2
performance in the complex feeds, fully consuming aldehydes while inhibiting
hydrogenation of olefins.

The comprehensive screening identifies 5Pt4Sn/TiO and CuZrO /SiO as promising
2 2 2
hydrogenation candidates of aldehydes for the integrated system. The compatibility
between syngas-to-oxygenates/olefins plus hydrogenation processes of aldehydes over
the above identified catalysts was further understood Sby different probe reactions.
Firstly, valeraldehyde hydrogenation with pure H and syngas was applied as model
2
reactions (Fig. 2b). It was found that the additioPn of Sn could avoid CO poisoning and
improve the activity of 5Pt/TiO , while comNparable performances were observed on the
2
Cu-based catalysts (Fig. S17). The Cu /SiO
2
showed high reactivity, but CuZrO
2
/SiO
2
was basically inactive, likely due to the different electronic states of the active Cu
species. This hypothesis was corroborated by CO pulse experiments, showing
significantly decreased CO adsorption on CuZrO /SiO as compared with those on the
2 2
other catalysts (Fig. 2c). The interfacial structures of small Cu nanoparticles on
ZrO (111), as indicated by combined PXRD, XPS, and HRTEM analyses (Figs. S18-
2
S20), were adopted as the catalyst model for the DFT investigations. Comparison of the
reaction coordinate of aldehyde hydrogenation pathways between Cu(111) and CuZrO
2
models revealed the much lower energy barriers of 0.64 eV on CuZrO instead of 1.65
2
eV on Cu(111) (Figs. 2d and S21, S22), agreeing well with the favorable formation of
alcohols on CuZrO . These thorough studies thus lay a solid foundation for the design
2
of more complicatedly integrated processes.

Process design for integrated catalysis system

Having successfully converted syngas to olefins and oxygenates by using Cs O-Co C-
2 2
Co catalysts, a more advanced integrated technology was developed, aiming to efficient
and precise regulating over the reaction pathways for direct syngas-to-C alcohol
4+
synthesis. This innovative approach employs cascaded heterogeneous
hydroformylation and hydrogenation catalysis within a single fixed-bed reactor in the
downstream of the syngas-to-oxygenates/olefins reactor. Our strategic combination of
different catalytic modules allows elimination of complicated separations from syngas
to the end products. To validate this concept, two chain reactors packing with three
well-designed catalysts of specific functions were designed to perform the selective
conversion of syngas into C alcohols under conditions of H /CO = 1.5, F = 130 ml
4+ 2
min-1, 210 oC (syngas-to-oxygenates/olefins), 140 oC (hydroformylation and
hydrogenation), and 3 MPa (Fig. 3a and Tables S5-S6). Notably, the cascade catalysis
featured by Co Mn Cs/C|Rh /3v-POPs-PPh |CuZrOS/SiO displayed the highest
0.5 0.1 1 3 2 2
alcohol selectivity of 81% at 15% CO conversion. Alcohols accounted for 95% in the
liquid products, with the shares of C and CP alcohols reaching 90% and 44%,
4+ 6+
respectively. Replacing Co
0.5
Mn
0.1
Cs/C wNith a carrier-modified catalyst CoMnCs/MC
further improved the performance. The CoMnCs/MC|Rh /POPs-BP-PPh |CuZrO /SiO
1 3 2 2
integrated system displayed 73% alcohol selectivity with C and C alcohols reaching
4+ 6+
69% and 50%, respectively, at 25% CO conversion, corresponding to an unprecedented
space-time yield (STY based on syngas-to-oxygenates/olefins) of C alcohols of 112
4+
g·kg -1·h-1.
cat A

Given the promising results on Co Mn Cs/C|Rh /3v-POPs-PPh |CuZrO /SiO ,
0.5 0.1 1 3 2 2
a
systematic examination of the key process parameters including H /CO ratio, gas
2
hourly space velocity (GHSV), bed temperature, and pressure was further conducted
(Tables S7-S10). The H /CO ratios significantly influenced CO conversion and the
2
selectivity of by-products (Table S7). Higher CO conversion was achieved with the
increase of H /CO ratios, resulting in a slight reduction in CO selectivity and an
2 2
increase in alkane selectivity. In contrast, C alcohol selectivity remains largely
4+
unaffected (68-75%) across a wide range of H /CO ratios. This stability in alcohol
2
selectivity is particularly advantageous for potential applications involving the
conversion of biomass- or coal-derived syngas. The impact of temperature on the
integrated catalysis was examined at an H /CO ratio of 1.5 (Table S8). CO conversion
2
significantly increased from 15% to 72% when the temperature was varied within 210-
240 oC, accompanied with a notable decrease in alcohol selectivity from 81% to 11%,
primarily due to over-hydrogenation as evidenced by the substantial formation of
alkanes. Nevertheless, several promising results were observed at lower temperatures.
For example, a high C alcohol selectivity of 73% was achieved at 210 oC, while the
4+
STY of C alcohols and total alcohols attained 119 g·kg ⁻¹·h⁻¹ and 143 g·kg ⁻¹·h⁻¹
4+ cat cat
at 230 oC, respectively. The impact of GHSV was further examined (Table S9). While
CO conversion consistently decreased, the alcohol selectivity remained relatively stable
and witnessed an apparent drop by 6% at 325 ml min-1. The pressure significantly
influenced catalytic performance (Table S10). CO conversion increased markedly from
1 to 3 MPa, leveling off at 8 MPa. Concurrently, C Salcohol selectivity increased
4+
substantially from 60% to 80%, while olefin selectivity decreased from 11 % to
negligible levels. Additionally, the ratio of normPal to isomeric (n/i) alcohols decreased
from 7 to 3 as pressure increased from 2 tNo 8 MPa. These results suggested that higher
pressure favored the formation of branched aldehydes, leading to their subsequent
hydrogenation into the corresponding isomeric alcohols. Finally, the long-term stability
of the developed Co Mn Cs/C│Rh /3v-POPs-PPh │20CuZnO /SiO integrated
0.5 0.1 1 3 2 2
catalytic system was evaluated under the reaction conditions of H /CO = 1.5, F = 130
2
ml min-1, 210 oC (syngas-to-oxygenates/olefins), 140 oC (hydroformylation and
hydrogenation), and 3 MPa, and a firmly stable performance for more than 130 h was
attained (Fig. 3b). ASF distribution clearly pointed to the favorable formation of C
4+
alcohols with an overall n/i ratio of 6 (Fig. 3c-3d, Fig. S3). In the integrated system, the
C -C products strongly deviate from the ASF linear distribution, and the chain growth
1 3
probability α increases from 0.65 to 0.68, indicating that the hydroformylation process
effectively modulates product distribution (Fig. S3). As the reaction pressure increased
from 3.0 to 8.0 MPa, the deviation of C -C products from the ASF linear distribution
1 3
became increasingly pronounced (Fig. S3e,f), while the chain growth probability α rose
from 0.68±0.01 to 0.72±0.01, demonstrating that elevated pressure enhances carbon
chain elongation and suppresses the formation of low-carbon products. Key
performance descriptors of this integrated process were compared with the previously
reported syngas-to-C alcohol conversion systems (Fig. 3e and Table S5),
4+
demonstrating the superiority in selectivity of C (80% vs. 45%) and C alcohols (50%
4+ 6+
vs. 33%), and productivity (STY of total, C and C alcohols reaching 143, 132, and
4+ 6+
119 g·kg -1·h-1, respectively). These excellent results can be well reproduced with
cat
minor variations (CO conversion within 14±1% and alcohol selectivity within 78±3%,
Table S11), thus demonstrating the great potential for industrial applications.

Comparative analysis of syngas-to-C alcohol synthesis pathways
4+
Currently, the production of C alcohols from syngas primarily relies on two routes:
4+
the heterogeneous hydroformylation and hydrogenation of C olefins obtained
3+
downstream of Fe-based Fischer-Tropsch synthesis, and the higher alcohol synthesis
directly from syngas (Fig. 4a). Our proposed process employs two fixed-bed reactors
to achieve an integrated, multi-stage conversion of syngas into C alcohols with
4+
unprecedented selectivity (~80%), alongside 10% C -C short-chain alcohols and 8%
1 3
C
5+
alkanes. Compared to the existing routes, this approach significantly reduces the
need for product separation, distillation, and reactor units (Fig. S23). Furthermore, it
can optimize waste heat utilization in industrial applications, resulting in substantial
energy savings and promoting the sustainable development of novel chemical processes.
The diversification and value-added nature of the products further stabilize market
value, offering substantial competitive advantages.

Fig. 4b compares CO selectivity across the three routes. In Route 1, Fe-based FTS
2
generates 20-40% CO during the synthesis of C olefins, which are subsequently
2 3+
converted into C alcohols via heterogeneous hydroformylation and hydrogenation.
4+
Route 2 employs Rh-based or modified methanol synthesis catalysts for direct HA
synthesis, producing less CO (1-10%) but achieving limited carbon chain growth, with
2
only 5-10% C alcohols. Modified Mo-based catalysts produce even higher CO
4+ 2
(~30%) while predominantly generating C -C alcohols. In contrast, our approach
1 3
achieves exceptional C alcohol selectivity (~80%) with CO₂ selectivity as low as ~1%,
4+
which has ultra-high carbon-efficiency (>95%, carbon-atom utilization efficiency from
CO to organic products other than CH
4
) by minimizing CH
4
and CO
2
formation and
dramatically reduces industrial production costs. By coupling residual CO with green
2
hydrogen via the reverse water-gas shift reaction to recycle syngas, the process might
approach net-zero CO emissions, significantly reducing greenhouse gas outputs.
2
Additionally, the catalyst demonstrates an oxygen-efficiency (oxygen-atom utilization
efficiency from CO to organic products) of 18%, a substantial improvement over the
HA synthesis and the industrial FTS paraffin production process (Fig. S24), where
oxygen-efficiency is just 6% and 1%, respectively (Fig. 4c). This enhanced efficiency
reduces CO costs and industrial wastewater generation, mitigating environmental
hazards.

Methods
Catalysts preparation

Co-based syngas-to-oxygenates/olefins catalysts

The modified Co/C catalysts were prepared by incipient wetness impregnation method.
According to the contents of active component of Co and additives of Mn, Cs, Ca, Ba,
Cr and Ni, series of mixed solution of Co(NO ) ·6H O (Aladdin, 99.99%) and
3 2 2
Mn(CH COO) ·6H O (Aladdin, 99.99%), Ca(NO ) ·6H O (Aladdin, 99.99%),
3 2 2 3 2 2
Ba(NO ) ·6H O (Aladdin, 99.99%), Cs(NO ) ·6SH O (Aladdin, 99.99%),
3 2 2 3 2 2
Cr(NO ) ·6H O (Aladdin, 99.99%) and Ni(NO ) ·6H O (Aladdin, 99.99%),
3 2 2 3 2 2
respectively, were prepared to add into the carboPn (Brilliant Tech Co. Ltd.). Loading of
Co and the other metal additives was 15 wNt.% and 0.03~3 wt.%, respectively (Co M N:
x y
M and N represent metal additives; x and y respectively represent the loading amounts
of additives M and N Catalysts include: 15Co, 15Co Cs, 15Co Cs, 15Co Cs,
0.03 0.1 0.3
15Co Mn, 15Co Mn, 15Co Mn Cs, 15Co Mn Cs, 15Co Mn Cs, 15Co Mn Ni,
0.5 1 0.5 0.1 1 0.1 1 0.3 0.5 1
15Co Mn Ni, 15Co Mn Ni, 15Co Mn Ca, 15Co Mn Ca, 15Co Mn Cr,
0.5 2 0.5 3 0.5 0.1 0.5 0.3 0.5 2
15Co 5Mn Cr, 15Co Mn Cr, 15Co Mn Cr, 15Co Mn Cr, 15Co Mn Ba,
0. 1 A1 1 1 2 2 2 0.5 0.1
15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba) .
0.5 0.3 0.5 0.5 0.5 1 0.5 2 0.5 3
Then, the catalysts were dried at room temperature and transferred to the oven at 50 oC
overnight. The catalyst precursors were further calcined in a flow of argon at 350 oC for
2 h. In addition, modified carbon carrier (MC) with enriched concentration of surface
oxygen groups was prepared as follows. The conventional carbon carrier was immersed
with 10% HNO in a round bottom flask and stirred at 60 oC for 6 h. After cooling to
3
room temperature, the solids were filtered, dried, and used for the loading of active
metals as stated previously. The Co-based syngas-to-oxygenates/olefins catalysts were
reduced in situ in fixed bed reactor for 10 h at 430 °C, 2000 h-1, 0.1 MPa, under an H
2
atmosphere before reaction. The catalyst composition for ICP characterization analysis
is shown in Table S12.

Rh-based heterogeneous hydroformylation catalysts

The Rh-based heterogeneous hydroformylation catalysts supported on porous organic
polymers (POPs) were prepared by post-loading method. 3v-POPs-PPh and POPs-
3
BP&PPh were previously reported to have been synthesized by the solvothermal
3
polymerization method (see references for preparation method of polymer carriers35,43)
For example, 0.35 g of 2v-BPa, 0.025 g of AIBN as an initiator, 10 mL of THF, and
0.65 g of 3V-PPh were introduced to a 30 mL autoclave under an argon atmosphere.
3
Following sealing, the solution was stirred for 1 h at room temperature and then left in
an oil bath at 100 °C for 24 h. After the insoluble was filtered, washed with THF and
dried under vacuum at 60 °C, the POPs-BP&PPh
3
could be obtained. The synthesis of
3v-POPs-PPh involved adding 0.025 g of AIBN, 10 mL Sof THF, and 1 g of 3v-PPh₃ to
3
a 30 mL autoclave under an argon atmosphere, and following the same steps.
1.2 g 3v-POPs-PPh or POPs-BP&PPh polPymer carrier was added to 100 mL
3 3
tetrahydrofuran (THF, 99%) containing 3N.8 mg Rh(CO) (acac) under N atmosphere.
2 2
The obtained solution was stirred in N atmosphere at room temperature for 24 h. The
2
catalysts were centrifugally separated, washed with excess THF, and dried under
vacuum at 60 oC to obtain the Rh /3v-POPs-PPh and Rh /POPs-BP&PPh catalysts.
1 3 1 3
Rh-based heterogeneous hydroformylation catalysts had no reduction treatment process.
The catalyst composition for ICP characterization analysis is shown in Table S12.

Hydrogenation catalysts

The Sn-modified Pt/TiO catalyst was prepared by ultrasonic-assisted impregnation
2
technique. Ethylene glycol (Aladdin, 99%) solution of stannous chloride (Aladdin, 99%)
and aqueous solution of chloroplatinic acid (Aladdin, 99%) were mixed. Subsequently,
a certain amount of TiO (Aladdin, 99%) carrier was weighed and dispersed in the above
2
mixed solution, and ultrasound was performed for 30 min. It was dried overnight in an
oven at 80 oC and then calcined in a muffle furnace at to 450 oC for 4 h (ramping 10 oC
min-1). The Pt-based hydrogenation catalysts were reduced in situ in fixed bed for 4 h
at 450 °C and 2000 h-1 under H atmosphere before reaction.
2
Cu/SiO and CuZrO /SiO catalysts were prepared by ammonia evaporation method.
2 2 2
The 0.3125 M Cu(NO ) ·3H O (Aladdin, 99%) solution was evenly stirred with SiO
3 2 2 2
(Aladdin, 99%) or ZrO (Aladdin, 99%), and then precipitated with 25% ammonia
2
solution (Aladdin, 99%) until the pH of the solution was 9~10, then heated at 80 oC and
washed the precipitate with deionized water. The prepared precipitate was dried at 120
oC for 10 h, and finally calcined in muffle furnace at to 450 oC for 4 h (ramping 2 oC
min-1). Cu-based hydrogenation catalysts were reduced in situ in fixed bed for 2 h at
260 °C, 2000 h-1, 0.1 MPa under H
2
atmosphere before reaction. The catalyst
composition for XRF characterization analysis is shown in Table S12.

RuPd/C and Ru/C catalysts were prepared by incipient wetness impregnation method.
According to the calculated content of active components Ru and Pd (RuCl ·3H O,
2 2
Aladdin, 99%; PdCl , Aladdin, 99%) a glycol solution (Aladdin, 99%) was prepared to
2
impregnate the activated carbon carrier. After drying at rSoom temperature, the catalyst
was transferred to the oven at 50 oC for overnight drying, and then roasted at 350 oC in
a flow of argon for 6 h to obtain the catalyst. PThe Ru-based hydrogenation catalysts
were reduced in situ in fixed bed for 4 h aNt 450 °C and 2000 h-1 under H atmosphere
2
before reaction.

Catalyst evaluation

Syngas to C long-chain alcohols
4+

The catalyst was evaluated in a self-made integrated system composed of two
consecutive stainless steel fixed-bed reactors with a reactor length of 450 mm and an
inner diameter of 9 mm (Fig. S25). In a typical test, 2 ml syngas-to-oxygenates/olefins
catalyst was loaded into the first reactor, and 1 ml heterogeneous hydroformylation
catalyst or/and 2 ml hydrogenation catalyst were placed to the second reactor, separated
by quartz sand and quartz cotton. The pressure of the reactors was controlled by a back
pressure valve located at the downstream of a cold trap after the second reactor, while
the bed temperatures were tuned by individual temperature controllers. After stabilized
for 24 h of reaction, the gaseous, liquid and solid products were periodically sampled
for analysis. The CO conversion was calculated by the inlet and outlet gas flow rates
measured by the mass flowmeter, and the product selectivity was calculated according
to the composition of the gas, liquid and solid products. Agilent 7890A gas
chromatograph with a Plot Q packed column and a HP-5 capillary column was used to
analyze the product compositions. Exhaust gas was analyzed online using a thermal
conductivity detector (TCD) and organic liquid products and solid was were analyzed
offline using a hydrogen flame ionization detector (FID). The secondary butanol as the
internal standard was used to analyze and calculate the components of the aqueous
phase products The organic phase products were calculated by the normalization
method with corrected peak area. The typical GC spectra of different products were
shown in Fig. S26. A comprehensive analysis, including liquid phases (organic and
aqueous), solid wax, and gaseous components, leads to excellent carbon balances
(generally within 100±5%).

Probe experiments

Valeraldehyde hydrogenation

Valeraldehyde hydrogenation was evaluated in a steel fixed-bed reactor with an inner
diameter of 9 mm and a length of 380 mm. 2 mPl hydrogenation catalyst was packed in
the middle of the reactor and pre-reduced Nby H under 260 ℃ (ramping rate 10 ℃ min-
2
1) at 0.1 MPa for 2 h. After cooling to 80 ℃, H or syngas (H /CO = 2/1) was introduced
2 2
and raised to 140 ℃ and 3.0 MPa. Valeraldehyde (Aladdin, 99%) was then admitted
with a syringe pump (flow rate of 0.01 mL min-1) for the hydrogenation reaction.
Agilent 7890N GC with Plot Q packed column and HP-5 capillary column was used to
analyze the products. Exhaust gas was analyzed online with a TCD detector and organic
liquid products were analyzed offline with an FID detector.

Water-gas shift

The water-gas shift (WGS) reaction was evaluated in the same setup as valeraldehyde
hydrogenation. Similar pre-reduction catalyst was applied. Then WGS reaction was
conducted by introducing N /CO mixture gas and water with a mass flow controller and
2
syringe pump, respectively, under 140 ℃ and 3.0 MPa. The reaction products were
analyzed on-line using an Agilent 7890N GC with a TDX-01 packed column and a TCD
detector.

Catalyst characterization

PXRD measurements were carried out on a PANalytical X'Pert3 powder X-ray
diffractometer. All tests were performed using Cu Kα radiation with operating
conditions of 40 kV and 40 mA. The samples were first ground to a fine powder in a
mortar and then tested on glass slides.

Elemental content testing of samples by Inductively Coupled Plasma (ICP) technique
on the Perkin Elmer ICP-OES 7300DV equipment. The metal content in the Cu-based
catalysts was determined by X-ray fluorescence spectroscopy (XRF).

The HRTEM images of the catalysts were collected on the Tecnai G2 F30 S-Twin
transmission electron microscope of FEI Company. The acceleration voltage was 300
kV, the line resolution was 0.1 nm, and the image point resolution was 0.2 nm.

The ac-HAADF-STEM and STEM images determination of catalyst samples was
acquired on the JEM-ARM200F STEM/TEM (resolution of 0.08 nm) and JEM-F200
instrument of JEOL, respectively. Sample was dispersed in EtOH and placed onto Cu
grids.

The CO pulse chemisorption experiment was caRrried out on the Zeton Altramira AMI-
300 chemisorption instrument. About 100N mg samples were packed into a U-shaped
tube using He as carrier gas at a flow rate of 30 mL min-1. The catalyst sample was first
heated to 120 ℃ at a heating rate of 10 ℃ min-1 in a flow of He, purged for 1 h, and
cooled to 50 ℃. Then, 10% CO/He mixture was quantitatively pulsing injected until
adsorption saturation, and the released CO was detected by a TCD detector.

The XPS tests were carried out on the Thermo Escalab 250Xi X-ray photoelectron
spectrometer of VG, using Al Kα as excitation source, accelerating voltage of 15 kV
and transmitting current of 10.8 mA.

DFT calculation methods

The theoretical calculation was completed by Vienna Ab Initio Simulation Package
(VASP.5.4.1) within density functional theory method. The standard PBE
pseudopotential of each element in projected augment plane-wave (PAW) method was
chosen. After an energy test convergence, the Cut-off energy was 450 eV. In order to
obtain the much more accurate energy and electronic structure, the spin polarization
was employed in all calculation. Gaussian method combined the electron broadening
of 0.05 eV was applied. For all structural optimization and property calculations, the
convergence thresholds of energy and force were 10-5 eV and 0.02 eV A-1, respectively.
Each transition state was found by climbing image nudged elastic band (CI-NEB)
method and further confirmed by the frequency analysis calculation. K-points sampling
scheme in Brillouin zone adopted the Monkhorst-Pack automatic sampling method and
the sampling density of K-point was 0.04 2*π/Angstrom for each structures model
which met the energy converging with K-points test.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This work reported the novel catalysis system for the conversion of syngas to C4+ long-chain alcohols. The system achieves a high selectivity of 80% C4+ long-chain alcohols with low CO2 and CH4 selectivities. Some interesting and important results were reported and discussed. However, the series connection of multiple catalysts causes an exceptionally complex reaction process, which may affect the industrial application prospects of the catalytic system. In addition, some conclusions have not received strong support and are not convincing. Therefore, there are some concerns that the authors should address well before further considering publication. The detailed comments are as follows:\n1. The catalytic performance should be discussed with reaction conditions in the abstract and conclusion.\n2. For a series of modified Co/C catalysts with different metal promoters (Mn, Cr, Ni, Ca, Ba, and Cs), the effect of promoters on selectivities of CO2 and CH4 should be discussed.\n3. The author suggested that interfacial sites of Co@Co2C structure were crucial for the preferential formation of alcohols. How to confirm that the catalyst forms a Co@Co2C core-shell structure during the reaction process?\n4. For DFT calculations, the detailed E, H, S, ZPE, G values for each IS, TS, and FS states should be listed in table. Also the coordinate files for optimized structures should be given in the supporting information.\n5. Does the lifespan of three catalysts, which are coupled in this work, differ? Will the mismatched lifespan of different catalysts limit the further industrial application of this catalytic system?\n6. I suggest the author also compare the STY of C4+alcohols with other catalytic systems reported in the literature.", "reviewer_2": "The authors report a nice study where they combine an optimized promoted Co-FT catalyst with a typical heterogeneous hydroformylation catalyst and a selective hydrogenation catalyst to convert syngas to C4+ alcohols with a remarkable selectivity at low CO conversions (below 15%) in a two-step process without intermediate separation. The low product yield is likely one of the barriers to implement this two-step process. Separation of the alcohols from water is costly –separation of water after the FT step is likely more efficient and indeed done industrially.\nThis is a nice experimental study and worth publishing. The experiments are supported by standard characterizations (XRD for some of the spent Co catalysts, XPS for some of the spent Co catalysts, TEM for the selected catalyst). BET, H2 chemisorption and TPR could be included for the optimized Co catalysts.\nSome DFT calculations are included for selected reactions on model surfaces (Co(111), Co island on Co2C, and a Cu13 cluster on ZrO2). The DFT calculations add little scientific value to the paper since they do not consider the relevant active sites, surface coverages or the relevant reaction steps. Also the introduction of a Cs atom to describe the effect of the Cs promotor is incorrect. Cs is likely present as Cs2O or Cs2CO3, and not all reactions will occur next to the promotor as proposed by the calculations. The quality of the paper would improve if the DFT calculations are not included.\nOn line 38, the authors mention iso-butanol as a valuable product, but the proposed process does not seem to produce significant amounts of isobutanol since the n/i selectivity in the hydroformylation is not controlled.\nIt would be interesting to include a Table with the state-of-the-art in C4+ alcohol synthesis in the SI to support the statement of ca. 20% on line 73.\nThe authors use subscripts to describe the catalysts (Co0.5Mn0.1Cs), but do not explain the subscripts. In the synthesis section, it is stated that all catalysts have 15 wt% Co loading. More details about the catalyst synthesis and composition (ICP?) could be included.\nEvidence for interfacial sites on Co@Co2C is not provided (line 147). Very little is known about the structure of the CoMnCs/C catalyst.", "reviewer_3": "The authors report an integration catalytic strategy for long-chain alcohol synthesis from syngas conversion using two separate reactors and a three-stage packed catalysts process, which realizes the tandem connection of syngas to long-chain oxygenates/olefins and the subsequent hydroformylation/hydrogenation to produce C4+ alcohols. The experiment achieves awfully excellent catalytic performance with 80% C4+ alcohols selectivity and 1% CO2 selectivity that surpasses the previous reports of the related syngas conversion to alcohols. Generally, the present work is featured by process integration and the optimized combination of several different types of functional catalysts, which is not significantly innovative with respect to the design concept because similar tandem patterns have been commonly reported. Besides, the author's discussion about the cognition of the cooperative catalysis between different modules is somewhat general. The specific comments or queries are listed as follows.\n(1)The authors presume that the CoMnCs/C catalysts used for syngas conversion to oxygenates/olefins possess the interfacial structure of CoCs@Co2C, plus Co(111) and Co@Co2C, which lacks characterization evidence. Does CoCs @ Co2C refer a core-shell structure? However, it was not obviously observed in the TEM image (Fig S4). In addition, this model also ignores the role of manganese promoters.\n(2)Personally, I think it is not of great significance to discuss the ecological benefits of the integrated catalytic strategy for syngas conversion in this work because the results are only obtained based on the small laboratory experiments without pilot or benchmark test.\n(3)In the text (Line 128 ~ 132), the authors mentioned that the single Mn and Cs modified Co-based catalysts would increase the selectivity of ROH and Olefins, but would reduce CO conversion. For example, the CO conversion over Co0.5Mn / C and Co0.1Cs / C were 20 % and 11 %, respectively, but that was increased to 29 % on Mn and Cs co-modified Co-based catalysts. Why?\n(4)The space-time yield of C4+ alcohols was calculated based on the single CoMnCs/C catalyst. This calculation method might be not reasonable because the other two modular catalysts also synergistically promote the formation of C4+ alcohols products.\n(5)The specific composition of the hydrogenation catalysts should be provided for deep understanding of the catalyst.\n(6)In the section of Catalyst evaluation, the pretreatment of the catalyst (e.g. reduction method) should be described in detail, because catalyst pretreatment has a great influence on the reaction performance. Moreover, in the characterization measurements, the authors should make clear how the samples were treated? What is the state of these samples (oxidic or reduced state, fresh or spent)?\n(7)In Fig 2b, it demonstrated CO (not valeraldehyde) conversion. This might be written error because the image is related the probe test of valeraldehyde hydrogenation.\n(8)From Table S6, it can be seen that the CO2 selectivity of Co0.5Mn0.1Cs / C | Rh1 / 3v-POPs-PPh3 | CuZrO2 / SiO2 should show an upward trend with the increase of reaction temperature. Why is the CO2 selectivity at 230℃lower than 220℃?"}, "author_response": "Journal: Nature Communcations\nManuscript ID: NCOMMS-25-14503A\nTitle: Selective conversion of syngas to C long-chain alcohols\n4+\nAuthor(s): Yihui Li, Ziang Zhao, Miao Jiang, Guoqing Wang, Zheng Li, Wei Lu,\nWenhao Cui, Rong Liu, Ronghe Lin, Yu Meng, Yuan Lyu, Li Yan, Hejun Zhu, Yunjie\nDing\nResponse to Reviewers\nReviewer #1:\nComment:\nThis work reported the novel catalysis system for the conversion of syngas to C long-\n4+\nchain alcohols. The system achieves a high selectivity of 80% C long-chain alcohols\n4+\nwith low CO and CH selectivities. Some interesting and important results were\n2 4\nreported and discussed. However, the series connection of multiple catalysts causes an\nexceptionally complex reaction process, which may affect the industrial application\nprospects of the catalytic system. In addition, some conclusions have not received\nstrong support and are not convincing. Therefore, there are some concerns that the\nauthors should address well before further considering publication. The detailed\ncomments are as follows:\nReply:\nWe warmly thanked the Reviewer #1 for recognizing the merits of this work and his/her\ncareful assessment. We also sincerely thank you for providing the critical and inspiring\ncomments, based on which we have now performed additional experiments and\ntheoretical calculations to fully address your concerns. A detailed point-to-point has\nnow been listed as follows:\n1) The catalytic performance should be discussed with reaction conditions in the\nabstract and conclusion.\nReply:\nThank you for the nice suggestion. Following your advice, we have provided an\nexpanded description of the catalytic performance by accommodating the relevant\nreaction conditions. Still, we keep the Abstract untouched because of the word’s limit\nof the journal.\n“The system achieves, i) an unprecedented selectivity of 80% C long-chain alcohols\n4+\nwith a remarkably low CO\n2\nselectivity of 1% at 17% CO conversion (typical conditions\nof H /CO = 1.5, F = 130 ml min-1, 210 oC (syngas-to-oxygenates/olefins) and 140 oC\n2\n(hydroformylation and hydrogenation)), ii) ultra-high 97% carbon-efficiency, and iii)\nimproved oxygen-efficiency, effectively addressing a key limitation of current syngas\nconversion technologies.”\n2) For a series of modified Co/C catalysts with different metal promoters (Mn, Cr, Ni,\nCa, Ba, and Cs), the effect of promoters on selectivities of CO and CH should be\n2 4\ndiscussed.\nReply:\nThank you for the insightful instruction, following which we have provided additional\na figure to show the impacts of different promoters on the CO and CH selectivity (Fig.\n2 4\nS2). As one can see, Mn additives could significantly reduce the methane selectivity\nfrom 25.3% to 10.2%, and CO selectivity is basically unchanged. After adding Cs\n2\nadditives, methane selectivity is significantly reduced from 25.3% to 8.4%, and CO\n2\nselectivity is increased from 0.9% to 2.1%. When Cs and Mn were added together, the\nmethane selectivity decreased to 6.6%, but the CO selectivity increased slightly to\n2\n2.7%. The addition of Ca and Ba additives significantly increased the methane\nselectivity. In addition, excessive Ni additives will increase the methane selectivity, but\nthe addition of Ca, Ba and Ni additives has no obvious effect for CO selectivity.\n2 4\npromoters.\nThe corresponding discussion has been briefly supplemented in the revision:\n“When 0.5 wt.% Mn was doped in Co/C, the selectivity of C oxygenates/C olefins\n4+ 3+\nwas markedly increased from 37% to 50% without compromising CO conversion (Fig.\n1b), which Mn was assumed to promote the C-C coupling and chain growth process,\nreducing CH selectivity from 22.0% to 10.2% (Table S1).”\n4\n“While the additions of Cr or Ni improved CO conversion but inhibited the formations\nof oxygenates/olefins, Ca and Ba additives promoted CH formation (Fig. S2), and great\n4\npromotional effect was observed with the addition of Cs (Fig. 1a). The regulation of\ndifferent metal additives scarcely impacted CO selectivity (all less than 5%).”\n2\n3) The author suggested that interfacial sites of Co@Co C structure were crucial for\n2\nthe preferential formation of alcohols. How to confirm that the catalyst forms a\nCo@Co C core-shell structure during the reaction process?\nWe thank the Reviewer for the insightful instruction. We sincerely apologize for any\nconfusion caused by our previous message. We should stress that here Co@Co C was\n2\nused to indicate the formation of interphases between Co and Co C entities, but not\n2\ncore-shell structures.\nIn order to clarify the catalyst structure, we have supplemented additional experiments\n(in situ PXRD, STEM and HRTEM) for a more detailed description (Fig. S5 and Fig.1).\nThe in situ PXRD tests of CoMnCs/C under different atmospheres revealed marked\ndifferences on the catalyst compositions. Specifically, only fcc-Co was formed subject\nto H reduction even up to 430 oC, but both fcc-Co and Co C were generated after\n2 2\nsyngas treatment at 210 oC at prolonged time. The latter phenomenon evidenced the\ncoexistence of both Co species, and indicated that Co C was likely in situ formed only\n2\nunder the syngas conversion conditions.\nFig. S5. In situ PXRD patterns of the CoMnCs/C catalysts under different conditions: (a) in H\n2\natmosphere (430 oC, 0.1 MPa); (b) syngas ambience (210 oC, 0.1 MPa).\nTo further visualize the more precise catalyst structures, we performed additional\nelectron microscopic analyses of the spent CoMnCs/C catalysts. First, we acquired\nSTEM with elemental color mapping image of the spent CoMnCs/C, showing the\napparent enrichment of carbon species around the Co nanoparticle (Fig. 1c). Then we\nalso performed a line scanning of an individual particle as shown in Fig. 1d. One can\nsee the relatively even distributions of Cs and Mn along the Co nanoparticle, possibly\nbecause of their lower contents. In contrast, the C signals were still quite strong beyond\nthe Co nanoparticles, further substantiating the color-mapping result. As carburization\ngradually accumulates, Co particles and the carbon layer undergo further reaction under\nreaction conditions and are gradually and partially converted into Co C. To validate this\n2\nhypothesis, we performed HRTEM test and analyzed the lattice fringes of an individual\nCo particle and the surroundings (Fig. 1e). We found that the Co(111) crystals and the\nperiphery was decorated by smaller Co C ensembles. Notably, the Co particle was only\n2\npartially decorated by several Co C ensembles, instead of fully covered by the latter.\nstructure to depict the key structure of the CoMnCs/C catalyst.\nFig. 1. Design of efficient syngas-to-oxygenates/olefins catalysts. (a) CO conversion vs. total\nselectivity of alcohols and olefins on carbon-supported Co catalysts with different promoters. (b)\nComparison on the syngas-to-oxygenates/olefins performance on representative Co-based catalysts.\nReaction conditions: 210 °C, 3.0 MPa, H /CO = 2.0, F = 65 ml min-1 (See Table S1 for details). (c-\n2\ne) STEM and HRTEM images of Co Mn Cs/C catalyst. (c) EDX mapping images. (d) Line\n0.5 0.1\nscanning profiles (inset). (f) The reaction coordinate of C H * desorption, hydrogenation, and CO\n5 10\ninsertion pathways on Co(111), Co@Co C, and CoCs@Co C models. Bader charge analysis were\n2 2\nshown in the inset.\nWe have now accommodated these new results and discussions into the revised\nmanuscript.\n“These observations strongly suggested the co-existence of both Co0 and in situ formed\nCo C on the catalyst surface, which was further confirmed by detailed high-resolution\n2\ntransmission in situ PXRD and electron microscopicy observations. The in situ PXRD\nexperiments verified the formation of both fcc-Co and Co C on CoMnCs/C under\n2\nsyngas treatment conditions but only fcc-Co after H reduction (Fig. S5), hinting the\n2\ncritical role of reaction atmospheres on the catalyst structure. Scanning transmission\nelectron microscopy (STEM) coupled with elemental color mapping image of the spent\ncatalyst unambiguously pointed to the surface enriching of carbon species around Co\nnanoparticle of CoMnCs/C catalyst (Fig. 1c). This was further supported by line-\nscanning of an individual nanoparticle, showing relatively even distributions of Cs and\nMn across the nanoparticles but much higher C signal than that of Co at the periphery\n(Fig. 1d). As carburization gradually accumulated, Co particles and the carbon layer\nunderwent further reaction under reaction conditions and were gradually and partially\nconverted into Co C. To validate this hypothesis, HRTEM image of the spent catalyst\n2\nwas acquired (Fig. 1e). Lattice fringe analysis revealed the structure of fcc-Co(111) in\nan individual particle decorated by small Co C ensembles (Fig. 1e). Noted that Co C\n2 2\nwas present as small patches on the Co surface, forming Co@Co C interphases, but did\n2\nnot fully cover the latter.”\n4) For DFT calculations, the detailed E, H, S, ZPE, G values for each IS, TS, and FS\nstates should be listed in table. Also the coordinate files for optimized structures\nshould be given in the supporting information.\nReply:\nWe thank the reviewers for their insightful and valuable suggestions. The detailed E, H,\nS, ZPE, G values for each IS, TS, and FS states in different calculation models have\nnow been listed in Table S3, and the coordinate files for all optimized structures were\ngiven in the Table S9-10.\nTable S3 The detailed E, H, S, ZPE, G values for each IS, TS, and FS states of the reaction pathway\nstudied in different calculation models\nModel Adsorbate E ZPE H S G\n*C H +*H -476.401 3.79037 4.29604 1.01725 3.27879\n5 10\nTS -474.539 3.7998 4.32034 1.089303 3.23104\n*C H +* -478.182 3.90762 4.423559 1.096589 3.32697\n5 11\n*C H +*H -481.493 4.09588 4.657957 1.214 3.443957\n5 11\nCo TS -481.256 4.17643 4.68669 1.107665 3.57902\n*C H +* -482.153 4.243895 4.72761 1.05287 3.67474\n5 12\n*C H +*CO -491.074 3.814761 4.439282 1.310257 3.129025\n5 10\nTS -489.132 3.78738 4.3921 1.29069 3.1015\n*C H CO -489.794 3.85222 4.44694 1.19525 3.25168\n5 10\n*C H +*H -1172.37 3.239188 3.414707 0.258252 3.156455\n5 10\nTS -1171.65 3.754593 4.239493 1.00823 3.231262\n*C H +* -1171.74 3.935586 4.452394 1.114208 3.338186\n5 11\n*C H +*H -1175.41 4.07887 4.593925 1.050358 3.543567\n5 11\nCo@Co C TS -1175.06 4.10611 4.64439 1.158693 3.485698\n2\n*C H +* -1175.75 4.244185 4.765384 1.139558 3.625826\n5 12\n*C H +*CO -1191.02 3.836483 4.4599 1.276726 3.183174\n5 10\nTS -1190.02 3.81345 4.411023 1.252404 3.158618\n*C H CO -1190.54 3.894902 4.475153 1.174496 3.300656\n5 10\n*C H +*H -1166.95 3.807738 4.322573 1.043739 3.278834\n5 10\nTS -1164.89 3.676979 4.168255 1.00371 3.164542\n*C H +* -1166.61 3.93566 4.440723 1.045434 3.395289\n5 11\n*C H +*H -1170.35 4.110334 4.643229 1.085104 3.558125\n5 11\nCoC @Co C TS -1169.4 4.077055 4.614339 1.120726 3.493614\nS 2\n*C H +* -1170.1 4.249638 4.76587 1.118895 3.646974\n5 12\n*C H +*CO -1179.76 3.769668 4.365136 1.203293 3.161843\n5 10\nTS -1178.7 3.791014 4.356055 1.105943 3.250112\n*C H CO -1178.79 3.830185 4.42587 1.216015 3.209856\n5 10\n*H O -434.871 0.622854 0.744382 0.269046 0.475336\n*OH+*H -434.788 0.521215 0.624136 0.172818 0.451318\n*CO+*OH+*H -450.507 0.698897 0.922948 0.420045 0.502903\nTS -449.488 0.711526 0.900765 0.396387 0.504378\n*COOH+*H -450.148 0.772586 0.968776 0.421367 0.547409\nTS -449.075 0.587511 0.734066 0.294878 0.439187\n*CO +*H -449.383 0.591737 0.761651 0.35426 0.407389\n2 2\nCu *H -427.223 0.294778 0.410038 0.280709 0.129328\n*2H -427.769 0.350252 0.37815 0.036417 0.341733\n*C H CHO+*H -529.36 4.661801 5.155494 1.065767 4.089727\n5 11\nTS -527.71 4.618257 5.08528 0.955278 4.130002\n*C H CH O+* -528.93 4.764797 5.170733 0.800561 4.370172\n5 11 2\n*C H CH O+*H -532.276 4.9056 5.351431 0.91401 4.43742\n5 11 2\nTS -532.106 4.87405 5.357289 0.99015 4.367139\n*C H CH OH+* -533.395 5.117547 5.586337 0.96158 4.624758\n5 11 2\n*H O -1744.2 0.634097 0.773856 0.318171 0.455685\n*OH+*H -1744.29 0.479353 0.58429 0.2266 0.35769\n*CO+*OH+*H -1757.15 0.53155 0.71298 0.357041 0.35594\nCu@ZrO TS -1756.09 0.568742 0.728394 0.31864 0.409753\n2\n*COOH+*H -1759.48 0.718562 0.860856 0.292235 0.568621\nTS -1758.98 0.627312 0.768796 0.289707 0.479089\n*CO +*H -1759.39 0.659887 0.813417 0.284827 0.52859\n2 2\n*H -1736.3 0.305213 0.373511 0.129036 0.244476\n*2H -1737.26 0.337568 0.379741 0.064128 0.315613\n*C H CHO+*H -1839.46 4.650485 5.047186 0.777926 4.26926\n5 11\nTS -1838.82 4.618898 5.04363 0.872195 4.171435\n*C H CH O+* -1839.38 4.786809 5.199093 0.85693 4.342163\n5 11 2\n*C H CH O+*H -1842.54 4.970997 5.416286 0.913088 4.503198\n5 11 2\nTS -1842.08 4.931647 5.352619 0.848944 4.503675\n*C H CH OH+* -1843.15 5.147832 5.560021 0.828798 4.731223\n5 11 2\nFig. S9. Illustrations of different configurations of *CO insertion into *C H species on the Co(111),\n5 10\nCo@Co and CoCs@Co C.\n2 2\nFig. S10. Illustrations of different configurations of *C H hydrogenation on the Co(111),\n5 10\nCo@Co C and CoCs@Co C.\n2 2\n5) Does the lifespan of three catalysts, which are coupled in this work, differ? Will the\nmismatched lifespan of different catalysts limit the further industrial application of\nthis catalytic system?\nReply:\nWe thank the reviewers for the insightful and valuable suggestions. Stability test of 130\nh for CoMnCs/C|3v-POPs-PPh |CuZrO /SiO tandem catalytic system was shown in\n3 2 2\nFig. 3b in the manuscript. To address the Reviewer’s concern, we have supplemented\nadditional 300 h stability experiments for both syngas-to-oxygenates/olefins and\nhydrogenation processes, showing relatively stable performances (Fig. R1-2). Based on\nour previous works (Chin. J. Catal., 2025, 73, 16-38; Reac. Kinet. Mech. Cat., 2015,\n116, 223-234; J. Mol. Catal., 2015, 404, 211-217.) 1-3, the hydroformylation catalyst\ncould run stably for 1000 and 500 h for hydroformylation of ethylene and propylene,\nrespectively. These preliminary results demonstrated the great potential of the proposed\ntandem processes for C alcohol synthesis from syngas, although we acknowledge that\n4+\nlonger durability tests in scale-up utilities are indispensable for realizing industrial\napplication in the future.\n80\n%\n/\ny\n60\ntiv\nitc\ne le 40 s lo\nh\nS o\n&\nc\nlA\nO20 X CO\nC\nX\n0\n0 20 40 60 80 100 120\nTime-of-steam / h\nFig. 3b. Stability test of CoMnCs/C|3v-POPs-PPh |CuZrO /SiO . Reaction conditions: 210 °C\n3 2 2\n(syngas-to-oxygenates/olefins) and 140 °C (hydroformylation/hydrogenation), 3.0 MPa, H /CO =\n2\n1.5, F = 130 ml min-1.\nFig. R1. Stability test of the Co Mn Cs/C catalysts Fischer-Tropsch synthetic (FTS). Reaction\n0.5 0.1\nconditions: P = 3.0 MPa, T = 210 ℃, GHSV = 2000 h-1, H /CO = 2.\n2 2\nproducts. Reaction conditions: P = 3.0 MPa, T = 140 ℃, H /CO = 2, F (H /CO = 2) = 30 ml min-1,\n2 2\nF (FTS products) = 0.02 ml min-1.\n6) I suggest the author also compare the STY of C alcohols with other catalytic\n4+\nsystems reported in the literature.\nReply:\nThank you for your valuable comments. We have now accommodated the STY of C\n4+\nalcohols in Table S5.\nTable S5. Catalytic performances of various catalysts for syngas conversion to oxygenates in the\nliteratures.\nT P H2/CO GHSV/ STYC4+OH\nCatalysts refs.\n/ °C / MPa / mol mol-1 ml g−1 h−1 / g kgcat -1 h-1\n210/140 a 3.0 1.5 1600 b 70.8 this work\nCoMnCs/C|Rh/3v-POPs-\n210/140 a 8.0 1.5 1600 b 89.7 this work\nPPh3|CuZrO2/SiO2\n230/140 a 3.0 1.5 1600 b 118.7 this work\nCoMnCs/MC|Rh/POPs-\n210/140 3.0 1.5 1600 b 111.9 this work\nBP&PPh3|CuZrO2/SiO2\nCu4Fe1Mg4-MMO 260 3.0 2.0 2400 b 101 4\n15Co5Fe/AC 220 3.0 2.0 2800 - 5\nER-MoS2-K 240 5.0 2.0 3000 b - 6\n50Mo/50Co 250 2.0 2.0 15 c - 7\nCs2O-Cu/ZnO/Al2O3 280 5.4 3.0 3750 - 8\nCo/CuZnO 250 0.2 2.0 45 c - 9\n15Co/SiO2 220 3.0 2.0 5600 - 10\n15Co/AC 220 3.0 2.0 2800 28 5\n15Co6.3SiO2/AC 220 3.0 2.0 500 - 10\n15Co1.9Al2O3/AC 220 3.0 2.0 500 - 10\n15Co/AC-H2-HNO3 210 3.0 2.0 2000 - 11\n15Co0.5Mn/AC 220 3.0 2.0 2000 50 12\n15Co0.5Mn1La/AC 220 3.0 2.0 2000 25 13\n15Co2Cr/AC 220 3.0 2.0 2000 - 14\n15Co0.1Ca/AC 220 3.0 2.0 900 - 15\nCo/MnOx@quasi-MOF-\n230 3.0 2.0 4500 b 18 16\nCo2Cu1 240 4.0 1.5 2000 - 18\nCo1Cu2Nb0.2 200 6.0 1.5 40 c - 19\nCo4Mn1K0.1 220 4.0 1.5 40 c 44 20\nCo1Cu1Mn1 240 6.0 2.0 2000 78 17\n2.1Ru-CoMn 220 6.0 1.0 2000 b 26 21\n1.1Rh-CoMn 220 6.0 1.0 2000 b 40 21\nCuCoAl|ZnO/ZrO2 250 5.0 2.0 4000 b 11 22\nCuZnAl-CoMn 220 6.0 2.0 2000 b - 23\nCoMn|CuZnAlZr 220 6.0 2.0 2000 b 23 24\nNaPr-CoRu/AomM\n200 1.2 2.0 - - 25\n|Co2CO8+PCy3\nZnCrAlOx |KNiMoS-\n250 5.0 1.0 3000 b - 26\nMMO-5\nCuCoAl|t-ZrO2 - - - - - 27\na 210 ℃ (syngas-to-oxygenates/olefins), 140 ℃ (hydroformylation/hydrogenation).\nb h−1.\nc sccm total flow.\nd estimated value\ne Alcohol and aldehyde.\nReviewer #2:\nComment:\nThe authors report a nice study where they combine an optimized promoted Co-FT\ncatalyst with a typical heterogeneous hydroformylation catalyst and a selective\nhydrogenation catalyst to convert syngas to C4+ alcohols with a remarkable selectivity\nat low CO conversions (below 15%) in a two-step process without intermediate\nseparation. The low product yield is likely one of the barriers to implement this two-\nstep process. Separation of the alcohols from water is costly separation of water after\nthe FT step is likely more efficient and indeed done industrially.\nThis is a nice experimental study and worth publishing. The experiments are supported\nby standard characterizations (XRD for some of the spent Co catalysts, XPS for some\nof the spent Co catalysts, TEM for the selected catalyst). BET, H2 chemisorption and\nTPR could be included for the optimized Co catalysts.\nReply:\nWe sincerely thanked the Reviewer # 2 for praising our work and reaccommodating the\npublication of this piece. We also thank you for your insightful comments and\nsuggestions, which are valuable for improving the quality of this work.\n1) Some DFT calculations are included for selected reactions on model surfaces\n(Co(111), Co island on Co C, and a Cu cluster on ZrO ). The DFT calculations\n2 13 2\nadd little scientific value to the paper since they do not consider the relevant active\nsites, surface coverages or the relevant reaction steps. Also, the introduction of a Cs\natom to describe the effect of the Cs promotor is incorrect. Cs is likely present as\nCs O or Cs CO , and not all reactions will occur next to the promotor as proposed\n2 2 3\nby the calculations. The quality of the paper would improve if the DFT calculations\nare not included.\nReply:\nWe agree with the Reviewer that the selection of models should be conducted with great\ncare. We also trust the rational combinations of experiments with computational studies\nvaluable for providing insights into the reaction mechanism. To strengthen the basis for\nthe DFT calculations, the following actions have been taken in the revision:\ni) We have conduced detailed structure analysis of CoMnCs/C catalyst by HRTEM and\nSTEM, based on which the rationale of Co@Co C was established. The Reviewer is\n2\nkindly asked to refer the detailed reply of Question 5.\nii) Secondly, for the key intermediates such as C H in the studied reaction, we\n5 10\nsystematically calculated multiple possible active sites, and then selected the most\nstable adsorption sites to conduct the relevant key elementary reaction calculations.\nBecause the calculation of coverage is complex and involves a large amount of work,\nwe did not consider the influence of coverage.\niii) We have simulated Csδ+ as the corresponding site for the model construction. For\nthe additive Cs, although we considered using Cs instead of Cs O, as many studies have\n2\nshown that it is mainly used as an electronic additive, we adopted the substitution of\nCs+ cations for Cs O in order to reduce the excessive complexity of the model here.\n2\nis in the +1-valence state. In addition, we supplemented a Cs O model (Fig. R5) and\n2\ncalculated the adsorption of the key intermediate C H . We found that the results of\n5 10\nthis model for the most stable adsorption of C H were relatively close to those of the\n5 10\nCs cation model shown as in Table S2. Therefore, we believe that the results of the Cs\ncation model adopted in this work are also convincing.\niv) Additionally, the detailed E, H, S, ZPE, G values for each IS, TS, and FS states in\ndifferent calculation models have now been listed in Table S3, and the coordinate files\nfor all optimized structures were given in the Supporting Information.\nTable S2. Bader charge of Cs in CoCs@Co C model\nModel\nelectrons in Cs gained or lost by Cs\nCoCs@Co C 8.228 -0.772\n5 10 2 2\nTable R1 adsorption energy of *C H at different sites in three Cs doping model\n5 10\nModels Adsorption energy (eV)\n-0.64\nCoCs@Co C\n2\n-0.91\n-0.52\nCo-Cs O@Co C\n2 2\n-0.95\nTable S3 The detailed E, H, S, ZPE, G values for each IS, TS, and FS states of the reaction pathway\nstudied in different calculation models\nModel Adsorbate E ZPE H S G\n*C H +*H -476.401 3.79037 4.29604 1.01725 3.27879\n5 10\nTS -474.539 3.7998 4.32034 1.089303 3.23104\n*C H +* -478.182 3.90762 4.423559 1.096589 3.32697\n5 11\n*C H +*H -481.493 4.09588 4.657957 1.214 3.443957\n5 11\nCo@Co C\n*C H +* -482.153 4.243895 4.72761 1.05287 3.67474\n5 12\n*C H +*CO -491.074 3.814761 4.439282 1.310257 3.129025\n5 10\nTS -489.132 3.78738 4.3921 1.29069 3.1015\n*C H CO -489.794 3.85222 4.44694 1.19525 3.25168\n5 10\n*C H +*H -1172.37 3.239188 3.414707 0.258252 3.156455\n5 10\nTS -1171.65 3.754593 4.239493 1.00823 3.231262\n*C H +* -1171.74 3.935586 4.452394 1.114208 3.338186\n5 11\n*C H +*H -1175.41 4.07887 4.593925 1.050358 3.543567\n5 11\nCo@Co C\n*C H +* -1175.75 4.244185 4.765384 1.139558 3.625826\n5 12\n*C H +*CO -1191.02 3.836483 4.4599 1.276726 3.183174\n5 10\nTS -1190.02 3.81345 4.411023 1.252404 3.158618\n*C H CO -1190.54 3.894902 4.475153 1.174496 3.300656\n5 10\n*C H +*H -1166.95 3.807738 4.322573 1.043739 3.278834\n5 10\nTS -1164.89 3.676979 4.168255 1.00371 3.164542\n*C H +* -1166.61 3.93566 4.440723 1.045434 3.395289\n5 11\n*C H +*H -1170.35 4.110334 4.643229 1.085104 3.558125\n5 11\nCoCs@Co C TS -1169.4 4.077055 4.614339 1.120726 3.493614\n2\n*C H +* -1170.1 4.249638 4.76587 1.118895 3.646974\n5 12\n*C H +*CO -1179.76 3.769668 4.365136 1.203293 3.161843\n5 10\nTS -1178.7 3.791014 4.356055 1.105943 3.250112\n*C H CO -1178.79 3.830185 4.42587 1.216015 3.209856\n5 10\n*H O -434.871 0.622854 0.744382 0.269046 0.475336\n*OH+*H -434.788 0.521215 0.624136 0.172818 0.451318\n*CO+*OH+*H -450.507 0.698897 0.922948 0.420045 0.502903\nTS -449.488 0.711526 0.900765 0.396387 0.504378\n*COOH+*H -450.148 0.772586 0.968776 0.421367 0.547409\nTS -449.075 0.587511 0.734066 0.294878 0.439187\n*CO +*H -449.383 0.591737 0.761651 0.35426 0.407389\n2 2\nCu *H -427.223 0.294778 0.410038 0.280709 0.129328\n*2H -427.769 0.350252 0.37815 0.036417 0.341733\n*C H CHO+*H -529.36 4.661801 5.155494 1.065767 4.089727\n5 11\nTS -527.71 4.618257 5.08528 0.955278 4.130002\n*C H CH O+* -528.93 4.764797 5.170733 0.800561 4.370172\n5 11 2\n*C H CH O+*H -532.276 4.9056 5.351431 0.91401 4.43742\n5 11 2\nTS -532.106 4.87405 5.357289 0.99015 4.367139\n*C H CH OH+* -533.395 5.117547 5.586337 0.96158 4.624758\n5 11 2\n*H O -1744.2 0.634097 0.773856 0.318171 0.455685\n*OH+*H -1744.29 0.479353 0.58429 0.2266 0.35769\n*CO+*OH+*H -1757.15 0.53155 0.71298 0.357041 0.35594\nTS -1756.09 0.568742 0.728394 0.31864 0.409753\n*COOH+*H -1759.48 0.718562 0.860856 0.292235 0.568621\nTS -1758.98 0.627312 0.768796 0.289707 0.479089\n*CO +*H -1759.39 0.659887 0.813417 0.284827 0.52859\n2 2\n*H -1736.3 0.305213 0.373511 0.129036 0.244476\n*2H -1737.26 0.337568 0.379741 0.064128 0.315613\n*C H CHO+*H -1839.46 4.650485 5.047186 0.777926 4.26926\n5 11\nTS -1838.82 4.618898 5.04363 0.872195 4.171435\n*C H CH O+* -1839.38 4.786809 5.199093 0.85693 4.342163\n5 11 2\n*C H CH O+*H -1842.54 4.970997 5.416286 0.913088 4.503198\n5 11 2\nTS -1842.08 4.931647 5.352619 0.848944 4.503675\n*C H CH OH+* -1843.15 5.147832 5.560021 0.828798 4.731223\n5 11 2\n2) On line 38, the authors mention iso-butanol as a valuable product, but the proposed\nprocess does not seem to produce significant amounts of isobutanol since the n/i\nselectivity in the hydroformylation is not controlled.\nReply:\nWe agree with the Reviewer that the formation of iso-butanol is not high compared with\nthat of n-butanol. Since this article is mainly aimed at C alcohols, and the wide use of\n4+\nC , C and C alcohols is generally outlined in the Introduction. As the Reviewer\n4 5-9 10-20\nmay have also noticed, the n/i ratios of butanol result from the hydroformylation of\npropylene. In addition, our previous works indicated that the n/i ratios can be finely\ntuned by engineering the phosphine ligands of the polymer support. The Reviewer is\nkindly asked to refer to our previous works (J. Catal.,2017, 353, 123-132, Nat.\nCommun., 2024, 15, 6967)28 29.\nWe have made revisions in the manuscript: “For instance, butanol, a key precursor in\nplastics (e.g., butyl acrylate and butyl acetate) and gasoline additive, The global markets\nfor n-butanol are projected to grow at a compound annual growth rate (CAGR) of 6.3%\nduring 2021-2032 reflecting their economic significance.”\n3) It would be interesting to include a Table with the state-of-the-art in C alcohol\n4+\nsynthesis in the SI to support the statement of ca. 20% on line 73.\nReply:\nWe thank the Reviewer for the valuable comments. The method of synthesizing C\n4+\nalcohols has been specifically described in Fig. S1, and the selectivity of C , C and\n2+ 4+\nC alcohols produced from syngas. Rh, Co, Cu, was summarized in Table S5. The total\n6+\nC alcohol selectivity of Fe- and Mo-based catalysts is about 20%. We found that the\n4+\nC alcohol selectivity of some catalysts is greater than 20%, but the products are\n4+\nmainly the mixture of alcohols and aldehydes.\nThese results were already mentioned in the previous manuscript:\n“Despite advances in bi- or multi-component state-of-the-art catalysts (MoS , Cu-Co,\n4+\nFig S1 and Table S5).”\nFig. S1. Different synthetic routes for the production of C long-chain alcohols. Commercialized\n4+\nand envisaged processes were highlighted by the red and blue boxes, respectively. Selectivity to C\n4+\nalcohols via differen routes was shown in the green box.\nTable S5. Catalytic performances of various catalysts for syngas conversion to oxygenates in the\nliteratures.\nH2/CO\nT P GHSV/ SC2+OH SC4+OH SC6+OH\nCatalysts / mol refs.\n/ °C / MPa ml g−1 h−1 / % / % / %\nmol-1\n210/140 a 3.0 1.5 1600 b 80.0 73.0 35.7 this work\nCoMnCs/C|Rh/3v-POPs-\n210/140 a 8.0 1.5 1600 b 86.3 79.9 45.5 this work\nPPh3|CuZrO2/SiO2\n230/140 a 3.0 1.5 1600 b 50.3 43.4 26.6 this work\nCoMnCs/MC|Rh/POPs-\n210/140 3.0 1.5 1600 b 72.7 68.5 50.1 this work\nBP&PPh3|CuZrO2/SiO2\nCu4Fe1Mg4-MMO 260 3.0 2.0 2400 b 18.6e ~13e - 4\n15Co5Fe/AC 220 3.0 2.0 2800 15.9e - 5.6e 5\nER-MoS2-K 240 5.0 2.0 3000 b 30.0e 1.7e 0.0 6\n50Mo/50Co 250 2.0 2.0 15 c 18.0e - - 7\nCs2O-Cu/ZnO/Al2O3 280 5.4 3.0 3750 15.0 de ~5.0e 0.0 8\nCo/CuZnO 250 0.2 2.0 45 c 42.1e - 0.0 9\n15Co/SiO2 220 3.0 2.0 5600 - - - 10\n15Co/AC 220 3.0 2.0 2800 16.5e - 9.4e 5\n15Co6.3SiO2/AC 220 3.0 2.0 500 18.6e - 10.9e 10\n15Co1.9Al2O3/AC 220 3.0 2.0 500 17.9e - 10.0e 10\n15Co/AC-H2-HNO3 210 3.0 2.0 2000 9.2e - 3.8e 11\n15Co0.5Mn/AC 220 3.0 2.0 2000 17.4e - 6.1e 12\n15Co0.5Mn1La/AC 220 3.0 2.0 2000 22.9e - 5.5e 13\n15Co2Cr/AC 220 3.0 2.0 2000 0.0 - 0.0 14\n15Co0.1Ca/AC 220 3.0 2.0 900 29.4e - 16.1e 15\nCo/MnOx@quasi-MOF-\n230 3.0 2.0 4500 b 36.0e ~20e ~14e 16\nCo2Cu1 240 4.0 1.5 2000 27.4e - - 18\nCo1Cu2Nb0.2 200 6.0 1.5 40 c - - - 19\nCo4Mn1K0.1 220 4.0 1.5 40 c ~52e ~35e ~22e 20\nCo1Cu1Mn1 240 6.0 2.0 2000 - - - 17\n2.1Ru-CoMn 220 6.0 1.0 2000 b 26.7e - - 21\n1.1Rh-CoMn 220 6.0 1.0 2000 b 31.7e - - 21\nCuCoAl|ZnO/ZrO2 250 5.0 2.0 4000 b 20.8e ~8e - 22\nCuZnAl-CoMn 220 6.0 2.0 2000 b 36.2e - ~3e 23\nCoMn|CuZnAlZr 220 6.0 2.0 2000 b 47.5e ~36e ~33 d,e 24\nNaPr-CoRu/AomM\n200 1.2 2.0 - - - 1.2e 25\n|Co2CO8+PCy3\nZnCrAlOx |KNiMoS-\n250 5.0 1.0 3000 b 44.0e 6.6e 0.0 26\nMMO-5\nCuCoAl|t-ZrO2 - - - - 51.6e - 0.0 27\na 210 ℃ (syngas-to-oxygenates/olefins), 140 ℃ (hydroformylation/hydrogenation).\nb h−1.\nc sccm total flow.\nd estimated value\ne Alcohol and aldehyde.\n4) The authors use subscripts to describe the catalysts (Co Mn Cs), but do not\n0.5 0.1\nexplain the subscripts. In the synthesis section, it is stated that all catalysts have 15\nwt% Co loading. More details about the catalyst synthesis and composition (ICP?) could be included.\nThank you for pointing out the relevant comments. We have now measured the metal\ncontents of the key catalysts by ICP and provided the results in Table S12. Relevant\nexplanations are provided in the manuscript:\n“The modified Co/C catalysts were prepared by incipient wetness impregnation method.\nLoadings of Co and the other metal additives was set as 15 wt.% and 0.03~3 wt.%\n(indicated by subscripts after the element), respectively.”\nTable S12. Synthetic approach and compositional for catalysts.\nSynthesis Elements of Nominal Measured\nCatalyst\nmethod composition Content / wt.% content / wt.%\nwetness\nCo/C Co 15 15.2 a\nimpregnation\nwetness Co 15 14.9 a\nCo Mn/C\n0.5\nimpregnation Mn 0.5 0.5 a\nwetness Co 15 15.1 a\nCo Cs/C\n0.1\nimpregnation Cs 0.1 0.1 a\nCo 15 14.9 a\nwetness\nCo Mn Cs/C Mn 0.5 0.5 a\n0.5 0.1\nimpregnation\nCs 0.1 0.1 a\nRh/3v-POPs-PPh post-loading Rh 0.125 0.1 a\n3\nammonia Cu 20 19.0 b\nCuZrO /SiO\n2 2\nevaporation Zr - 28.0 b\nammonia\nCu/SiO Cu 20 22.0 b\n2\nevaporation\na Determined from ICP-OES\nb Determined from XRF\n5) Evidence for interfacial sites on Co@Co C is not provided (line 147). Very little is\n2\nknown about the structure of the CoMnCs/C catalyst.\nReply:\nWe thank the Reviewer for the insightful instruction. We sincerely apologize for any\nconfusion caused by our previous message. We should stress that here Co@Co C was\n2\nused to indicate the formation of interphases between Co and Co C entities, but not\n2\ncore-shell structures.\nIn order to clarify the catalyst structure, we have supplemented additional experiments\n(in situ PXRD, STEM and HRTEM) for a more detailed description (Fig. S5 and Fig.1).\nThe in situ PXRD tests of CoMnCs/C under different atmospheres revealed marked\ndifferences on the catalyst compositions. Specifically, only fcc-Co was formed subject\nto H reduction even up to 430 oC, but both fcc-Co and Co C were generated after\n2 2\nsyngas treatment at 210 oC at prolonged time. The latter phenomenon evidenced the\ncoexistence of both Co species, and indicated that Co C was likely in situ formed only\n2\nunder the syngas conversion conditions.\nFig. S5. In situ PXRD patterns of the CoMnCs/C catalysts under different conditions: (a) in H\n2\natmosphere (430 oC, 0.1 MPa); (b) syngas ambience (210 oC, 0.1 MPa).\nTo further visualize the more precise catalyst structures, we performed additional\nelectron microscopic analyses of the spent CoMnCs/C catalysts. First, we acquired\nSTEM with elemental color mapping image of the spent CoMnCs/C, showing the\napparent enrichment of carbon species around the Co nanoparticle (Fig. 1c). Then we\nalso performed a line scanning of an individual particle as shown in Fig. 1d. One can\nsee the relatively even distributions of Cs and Mn along the Co nanoparticle, possibly\nbecause of their lower contents. In contrast, the C signals were still quite strong beyond\nthe Co nanoparticles, further substantiating the color-mapping result. As carburization\ngradually accumulates, Co particles and the carbon layer undergo further reaction under\nreaction conditions and are gradually and partially converted into Co C. To validate this\n2\nhypothesis, we performed HRTEM test and analyzed the lattice fringes of an individual\nCo particle and the surroundings (Fig. 1e). We found that the Co(111) crystals and the\nperiphery was decorated by smaller Co Censembles. Notably, the Co particle was only\n2\npartially decorated by several Co C ensembles, instead of fully covered by the latter.\nstructure to depict the key structure of the CoMnCs/C catalyst.\nFig. 1. Design of efficient syngas-to-oxygenates/olefins catalysts. (a) CO conversion vs. total\nselectivity of alcohols and olefins on carbon-supported Co catalysts with different promoters. (b)\nComparison on the syngas-to-oxygenates/olefins performance on representative Co-based catalysts.\nReaction conditions: 210 °C, 3.0 MPa, H /CO = 2.0, F = 65 ml min-1 (See Table S1 for details). (c-\n2\ne) STEM and HRTEM images of Co Mn Cs/C catalyst. (c) EDX mapping images. (d) Line\n0.5 0.1\nscanning profiles (inset). (f) The reaction coordinate of C H * desorption, hydrogenation, and CO\n5 10\ninsertion pathways on Co(111), Co@Co C, and CoCs@Co C models. Bader charge analysis were\n2 2\nshown in the inset.\nWe have now accommodated these new results and discussions into the revised\nmanuscript.\n“These observations strongly suggested the co-existence of both Co0 and in situ formed\nCo C on the catalyst surface, which was further confirmed by detailed high-resolution\n2\ntransmission in situ PXRD and electron microscopicy observations. The in situ PXRD\nexperiments verified the formation of both fcc-Co and Co C on CoMnCs/C under\n2\nsyngas treatment conditions but only fcc-Co after H reduction (Fig. S5), hinting the\n2\ncritical role of reaction atmospheres on the catalyst structure. Scanning transmission\nelectron microscopy (STEM) coupled with elemental color mapping image of the spent\ncatalyst unambiguously pointed to the surface enriching of carbon species around Co\nnanoparticle of CoMnCs/C catalyst (Fig. 1c). This was further supported by line-\nscanning of an individual nanoparticle, showing relatively even distributions of Cs and\nMn across the nanoparticles but much higher C signal than that of Co at the periphery\n(Fig. 1d). As carburization gradually accumulated, Co particles and the carbon layer\nunderwent further reaction under reaction conditions and were gradually and partially\nconverted into Co C. To validate this hypothesis, HRTEM image of the spent catalyst\n2\nwas acquired (Fig. 1e). Lattice fringe analysis revealed the structure of fcc-Co(111) in\nan individual particle decorated by small Co C ensembles (Fig. 1e). Noted that Co C\n2 2\nwas present as small patches on the Co surface, forming Co@Co C interphases, but did\n2\nnot fully cover the latter.”\nReviewer #3:\nComment:\nThe authors report an integration catalytic strategy for long-chain alcohol synthesis\nfrom syngas conversion using two separate reactors and a three-stage packed catalysts\nprocess, which realizes the tandem connection of syngas to long-chain\noxygenates/olefins and the subsequent hydroformylation/hydrogenation to produce\nC4+ alcohols. The experiment achieves awfully excellent catalytic performance with\n80% C4+ alcohols selectivity and 1% CO2 selectivity that surpasses the previous\nreports of the related syngas conversion to alcohols. Generally, the present work is\nfeatured by process integration and the optimized combination of several different types\nof functional catalysts, which is not significantly innovative with respect to the design\nconcept because similar tandem patterns have been commonly reported. Besides, the\nauthor's discussion about the cognition of the cooperative catalysis between different\nmodules is somewhat general. The specific comments or queries are listed as follows.\nReply:\nWe sincerely appreciate the time and effort the Reviewer #3 have taken to review our\nmanuscript. Your constructive feedback is valuable in helping us refine and improve\nour work. We also thank you for recognizing the merits of our work. Despite of the\noutstanding catalytic performance reached in this work, we kindly remind the Reviewer\nfor the following three key innovative aspects:\ni) It is the first work targeting C alcohols synthesis from syngas. A significant boost\n4+\nin C alcohol selectivity (80%) at a reasonable CO conversion has been reached as\n4+\ncompared with the previous works (Table S5).\nii) Although tandem catalysis has been adopted in syngas conversions, to the best of\nour knowledge, it is the first report that combines three distinctive reactions (syngas-\nto-oxygenates/olefins + hydroformylation + hydrogenation) in two reactors for syngas\nconversion. This is a new catalytic process specifically designed for higher-alcohol\nsynthesis with unprecedented selectivity. In particular, it is also the first that the\nCoCs@Co C catalyst was proposed for the effective targeted synthesis of oxygenates\n2\nand olefins.\niii) We have also examined the complex compatibility of the three significantly different\ncatalytic modules by combining broad screening of catalytic materials, probe reactions,\nand DFT simulations. This innovative approach can provide a rationale for the catalyst\ndesign with complicate feeds in other tandem reactions.\n1) The authors presume that the CoMnCs/C catalysts used for syngas conversion to\noxygenates/olefins possess the interfacial structure of CoCs@Co C, plus Co(111)\n2\nand Co@Co C, which lacks characterization evidence. Does CoCs@Co C refer a\n2 2\ncore-shell structure? However, it was not obviously observed in the TEM image\n(Fig S4). In addition, this model also ignores the role of manganese promoters.\nReply:\nWe thank the Reviewer for the insightful instruction. We sincerely apologize for any\nconfusion caused by our previous message. We should stress that here Co@Co C was\n2\nused to indicate the formation of interphases between Co and Co C entities, but not\n2\ncore-shell structures.\nIn order to clarify the catalyst structure, we have supplemented additional experiments\n(in situ PXRD, STEM and HRTEM) for a more detailed description (Fig. S5 and Fig.1).\nThe in situ PXRD tests of CoMnCs/C under different atmospheres revealed marked\ndifferences on the catalyst compositions. Specifically, only fcc-Co was formed subject\nto H reduction even up to 430 oC, but both fcc-Co and Co C were generated after\n2 2\nsyngas treatment at 210 oC at prolonged time. The latter phenomenon evidenced the\ncoexistence of both Co species, and indicated that Co C was likely in situ formed only\n2\nunder the syngas conversion conditions.\nFig. S5. In situ PXRD patterns of the CoMnCs/C catalysts under different conditions: (a) in H\n2\natmosphere (430 oC, 0.1 MPa); (b) syngas ambience (210 oC, 0.1 MPa).\nFig. 1. Design of efficient syngas-to-oxygenates/olefins catalysts. (a) CO conversion vs. total\nselectivity of alcohols and olefins on carbon-supported Co catalysts with different promoters. (b)\nComparison on the syngas-to-oxygenates/olefins performance on representative Co-based catalysts.\nReaction conditions: 210 °C, 3.0 MPa, H /CO = 2.0, F = 65 ml min-1 (See Table S1 for details). (c-\n2\ne) STEM and HRTEM images of Co Mn Cs/C catalyst. (c) EDX mapping images. (d) Line\n0.5 0.1\nscanning profiles (inset). (f) The reaction coordinate of C H * desorption, hydrogenation, and CO\n5 10\ninsertion pathways on Co(111), Co@Co C, and CoCs@Co C models. Bader charge analysis were\n2 2\nshown in the inset.\nTo further visualize the more precise catalyst structures, we performed additional\nelectron microscopic analyses of the spent CoMnCs/C catalysts. First, we acquired\nSTEM with elemental color mapping image of the spent CoMnCs/C, showing the\napparent enrichment of carbon species around the Co nanoparticle (Fig. 1c). Then we\nalso performed a line scanning of an individual particle as shown in Fig. 1d. One can\nsee the relatively even distributions of Cs and Mn along the Co nanoparticle, possibly\nbecause of their lower contents. In contrast, the C signals were still quite strong beyond\nthe Co nanoparticles, further substantiating the color-mapping result. As carburization\ngradually accumulates, Co particles and the carbon layer undergo further reaction under\nreaction conditions and are gradually and partially converted into Co C. To validate this\n2\nhypothesis, we performed HRTEM test and analyzed the lattice fringes of an individual\nCo particle and the surroundings (Fig. 1e). We found that the Co(111) crystals and the\nperiphery was decorated by smaller Co Censembles. Notably, the Co particle was only\n2\npartially decorated by several Co C ensembles, instead of fully covered by the latter.\nstructure to depict the key structure of the CoMnCs/C catalyst.\nWe have now accommodated these new results and discussions into the revised\nmanuscript.\n“These observations strongly suggested the co-existence of both Co0 and in situ formed\nCo C on the catalyst surface, which was further confirmed by detailed high-resolution\n2\ntransmission in situ PXRD and electron microscopicy observations. The in situ PXRD\nexperiments verified the formation of both fcc-Co and Co C on CoMnCs/C under\n2\nsyngas treatment conditions but only fcc-Co after H reduction (Fig. S5), hinting the\n2\ncritical role of reaction atmospheres on the catalyst structure. Scanning transmission\nelectron microscopy (STEM) coupled with elemental color mapping image of the spent\ncatalyst unambiguously pointed to the surface enriching of carbon species around Co\nnanoparticle of CoMnCs/C catalyst (Fig. 1c). This was further supported by line-\nscanning of an individual nanoparticle, showing relatively even distributions of Cs and\nMn across the nanoparticles but much higher C signal than that of Co at the periphery\n(Fig. 1d). As carburization gradually accumulated, Co particles and the carbon layer\nunderwent further reaction under reaction conditions and were gradually and partially\nconverted into Co C. To validate this hypothesis, HRTEM image of the spent catalyst\n2\nwas acquired (Fig. 1e). Lattice fringe analysis revealed the structure of fcc-Co(111) in\nan individual particle decorated by small Co C ensembles (Fig. 1e). Noted that Co C\n2 2\nwas present as small patches on the Co surface, forming Co@Co C interphases, but did\n2\nnot fully cover the latter. To understand the individual roles of Mn and Cs on the catalyst\nstructure, the STEM with line-scanning images of Co/C, CoMn/C, and CoCs/C\ncatalysts, together with their corresponding HRTEM images, were acquired (Fig. S6).\nThese results showed that the addition of Mn alone also promoted the clear carbon\nenrichment on Co particles and in situ formation of Co@Co C structure during FTS\n2\nreaction, which were not observed on Co/C and CoCs/C. Considering that Cs was\nmainly enriched on Co nanoparticles for the best-performing CoMnCs/C catalyst\n(potentially existing as Cs+ species due to the nature of electronic promoter, also\nsupported by DFT calculations in Table S2-3 and Fig. S9-10), the CoCs@Co C model\n2\nwas constructed for further simulation.”\nFig. S6. (a-d) STEM images, (e-g) Line scanning profiles and (i-l) HRTEM images of CoMnCs/C,\nCoMn/C, CoCs/C and Co/C\n2) Personally, I think it is not of great significance to discuss the ecological benefits of\nthe integrated catalytic strategy for syngas conversion in this work because the\nresults are only obtained based on the small laboratory experiments without pilot or\nbenchmark test.\nReply:\nWe fully agree with the Reviewer that the lab-scale experiments are far from enough to\nreach a solid conclusion on the ecological benefits. In fact, we have previously\nconducted a life cycle analysis of this newly established process. But for the same\nreason, we decided to remove it and focus more on the comparative analysis of different\nsyngas-to-C alcohol technologies. We trust this information is still useful to give the\n4+\nreaders a broader landscape of the technological developments.\nConsidering your kind advice, we have decided to lower our tune of this section and\nfocus more on the comparison on the different process. The following two actions are\ntaken in the revision:\nWe have replaced the section title “Ecological benefits” with “Comparative analysis\nof syngas-to-C alcohol synthesis pathways”.\n4+\nWe have removed the sentence related to ecological implication:\n“From an ecological perspective, the system provides remarkable benefits by\nminimizing CO emissions. Fig. 4b compares CO selectivity across the three routes.”\n2 2\n3) In the text (Line 128~132), the authors mentioned that the single Mn and Cs\nmodified Co-based catalysts would increase the selectivity of ROH and Olefins, but\nwould reduce CO conversion. For example, the CO conversion over Co Mn/C and\n0.5\nCo Cs/C were 20% and 11%, respectively, but that was increased to 29% on Mn\n0.1\nand Cs co-modified Co-based catalysts. Why?\nReply:\nWe thank the Reviewer for the valuable comments. Mn additives could form a relative\n“C-rich and H-lean” surface chemical environment, so that the Co@Co C interface\n2\ncould be in situ reconstructed during the reaction process, and the olefines and alcohols\nselectivity could be improved (ACS Catal., 2017, 8, 228-241) 12.\nFurthermore, the co-addition of Cs and Mn promoted the dispersion of Co species as\ncompared with the counterparts with individual promoters. Based on the TEM analysis\nof the catalysts after the reaction, it was observed that the particle size of CoMnCs/C\ncatalyst was significantly reduced (D = 6.9 nm), while CoMn/C and CoCs/C catalysts\nshowed much large mean particle sizes, 8.6 and 8.0 nm, respectively. The increased\ndispersion of the former may thereby increase the exposed Co nanoparticle active sites\nand improve the catalytic activity.\nIn the manuscript, we have provided corresponding supplements：\n“In addition, the addition of Cs promoted the dispersion of Co species. Statistic particle\ncounting from TEM images of the spent catalysts revealed that, the particle size of\nCoMnCs/C catalyst was significantly smaller than the counterparts with individual\npromoters (D = 6.9 vs. 8.0, 8.6 nm, Fig. S7). The better dispersion could increase the\nexposed Co nanoparticle active sites, thereby improving the catalytic activity.”\nFig. S7. (a-c) STEM image of the CoMn/C, CoCs/C and CoMnCs/C catalysts at low magnification.\n(d-f) Particle distribution over the CoMn/C, CoCs/C and CoMnCs/C catalysts, respectively.\n4) The space-time yield of C alcohols was calculated based on the single CoMnCs/C\n4+\ncatalyst. This calculation method might be not reasonable because the other two\nmodular catalysts also synergistically promote the formation of C alcohols\n4+\nproducts.\nReply:\nWe thank the reviewers for their insightful suggestions. In response to the Reviewer's\nsuggestion, we have provided STY calculated based on all catalysts. The Reviewer is\nkindly asked to refer to Tables S6-S10.\nTable S6. The catalytic performances of different combinations of catalysts in the tandem system\nfor the syngas-to-C alcohols conversion.\n4+\nCatalysts S S STY STY STY STY\nC4+OH C6+OH OH C2+OH C4+OH C6+OH\ng kg -1 h-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1\n% % cat cat cat cat\nA 56.4 33.7 78.3 76.7 70.8 32.0\nB 68.5 50.1 119.4 118.4 111.9 74.3\nC 73.0 35.7 77.1 72.8 59.2 29.9\nA: Co0.5Mn0.1Cs/C|Rh/3v-POPs-PPh |5Pt4Sn/TiO .\n3 2\nB: Co0.5Mn0.1Cs/MC|Rh/3v-POPs-BP&PPh |CuZrO /SiO .\n3 2 2\nC: Co0.5Mn0.1Cs/C|Rh/3v-POPs-PPh |CuZrO /SiO .\n3 2 2\nReaction conditions: H /CO = 1.5, F = 130 ml min-1, T = 210 ℃ (syngas-to-oxygenates/olefins), T\n2\n= 140 ℃ (hydroformylation/hydrogenation), and P = 3 MPa.\nTable S7. Influence of H /CO ratios on the catalytic performances of Co Mn Cs/C|Rh/3v-POPs-\n2 0.5 0.1\nPPh |CuZrO /SiO tandem system for the syngas-to-C alcohols conversion.\n3 2 2 4+\nH /CO S S STY STY STY STY\nmol mol-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1\n% % cat cat cat cat\n1/2 75.0 46.8 31.4 30.2 28.7 14.3\n1/1 67.9 43.0 41.9 39.3 34.0 12.7\n3/2 73.0 35.7 78.3 76.7 70.8 32.0\n2/1 69.5 29.2 68.1 67.8 59.2 23.0\n3/1 69.2 39.1 58.5 55.9 52.2 24.2\nReaction conditions: F = 130 ml min-1, 210 oC (syngas-to-oxygenates/olefins), 140 oC\n(hydroformylation/hydrogenation), and 3 MPa.\nTable S8. Influence of bed temperatures of the syngas-to-oxygenates/olefins reactor on the catalytic\nperformances of Co Mn Cs/C|Rh/3v-POPs-PPh |CuZrO /SiO tandem system for the syngas-to-\n0.5 0.1 3 2 2\nC alcohols conversion.\n4+\nS S STY STY STY STY\nC4+OH C6+OH OH C2+OH C4+OH C6+OH\nT / ℃\ng kg -1 h-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1\n% % cat cat cat cat\n210 73.0 35.7 78.3 76.7 70.8 32.0\n220 52.8 37.1 128.8 126.9 108.7 76.4\n230 43.4 26.3 143.3 132.6 118.7 60.5\n240 9.0 5.3 50.9 47.9 41.5 14.3\nReaction conditions: H /CO = 1.5, F = 130 ml min-1, 140 ℃ (hydroformylation/hydrogenation), and\n2\nTable S9. Influence of GHSV (based on all catalysts) on the catalytic performances of\nCo Mn Cs/C|Rh/3v-POPs-PPh |CuZrO /SiO tandem system for the syngas-to-C alcohols\n0.5 0.1 3 2 2 4+\nconversion.\nS S STY STY STY STY\nC4+OH C6+OH OH C2+OH C4+OH C6+OH\nGHSV / h-1\ng kg -1 h-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1\n% % cat cat cat cat\n800 67.8 42.3 70.2 63.7 60.6 27.4\n1600 73.0 35.7 78.3 76.7 70.8 32.0\n2400 75.8 31.5 75.7 74.5 68.5 15.7\n3200 74.8 50.8 76.3 75.4 71.5 43.4\n4000 60.5 43.3 67.2 62.8 55.0 30.2\nReaction conditions: H /CO = 1.5, 210 ℃ (syngas-to-oxygenates/olefins), 140 ℃\n2\n(hydroformylation/hydrogenation), and 3 MPa.\nTable S10. Influence of pressures on the catalytic performances of Co Mn Cs/C|Rh/3v-POPs-\n0.5 0.1\nPPh |CuZrO /SiO tandem system for the syngas-to-C alcohols conversion.\n3 2 2 4+\nS S STY STY STY STY\nC4+OH C6+OH OH C2+OH C4+OH C6+OH\nP/ MPa\ng kg -1 h-1 g kg -1 h-1 g kg -1 h-1 g kg -1 h-1\n% % cat cat cat cat\n1 59.8 41.6 17.8 10.4 16.1 17.7\n2 72.0 50.3 30.1 29.7 27.6 17.6\n3 73.0 35.7 78.3 76.7 70.8 32.0\n8 79.8 45.9 97.1 96.7 89.7 45.7\nReaction conditions: H /CO = 1.5, F = 130 ml min-1, 210 ℃ (syngas-to-oxygenates/olefins),\n2\n140 ℃ (hydroformylation/hydrogenation).\n5) The specific composition of the hydrogenation catalysts should be provided for\ndeep understanding of the catalyst.\nReply:\nThank you for the relevant comments. We have supplemented the synthesis method and\ncomposition of Cu-based hydrogenation catalysts in the manuscript (Table S12).\nTable S12. Synthetic approach and compositional for catalysts.\nSynthesis Elements of Nominal Measured\nCatalyst\nmethod composition Content / wt.% content / wt.%\nwetness\nCo/C Co 15 15.2 a\nimpregnation\nwetness Co 15 14.9 a\nCo Mn/C\n0.5\nimpregnation Mn 0.5 0.5 a\nwetness Co 15 15.1 a\nCo Cs/C\n0.1\nimpregnation Cs 0.1 0.1 a\nwetness Co 15 14.9 a\nCo Mn Cs/C\n0.5 0.1\nimpregnation Mn 0.5 0.5 a\nCs 0.1 0.1 a\nRh/3v-POPs-PPh post-loading Rh 0.125 0.1 a\n3\nammonia Cu 20 19.0 b\nCuZrO /SiO\n2 2\nevaporation Zr - 28.0 b\nammonia\nCu/SiO Cu 20 22.0 b\n2\nevaporation\na Determined from ICP-OES.\nb Determined from XRF.\n6) In the section of Catalyst evaluation, the pretreatment of the catalyst (e.g. reduction\nmethod) should be described in detail, because catalyst pretreatment has a great\ninfluence on the reaction performance. Moreover, in the characterization\nmeasurements, the authors should make clear how the samples were treated? What\nis the state of these samples (oxidic or reduced state, fresh or spent)?\nReply:\nWe thank the Reviewers for the valuable comments, which we have supplemented in\nthe catalyst evaluation, as detailed below:\n“The Co-based syngas-to-oxygenates/olefins catalysts were reduced in situ in a fixed-\nbed reactor for 10 h at 430 °C, 2000 h-1, 0.1 MPa, under an H atmosphere before\n2\nreaction.\nRh-based heterogeneous hydroformylation catalysts had no reduction treatment process.\nCu-based hydrogenation catalysts were reduced in situ in fixed bed for 2 h at 260 °C,\n2000 h-1, 0.1 MPa under H atmosphere before reaction.\nh at 450 °C and 2000 h-1 under H atmosphere before reaction.”\nannotated in the corresponding figures.\nWe have supplemented in the characterization measurements, as detailed below:\n“Elemental content testing of samples by Inductively Coupled Plasma (ICP) technique\non the Perkin Elmer ICP-OES 7300DV equipment. The metal content in the Cu-based\ncatalysts was determined by X-ray fluorescence spectroscopy (XRF).\nThe ac-HAADF-STEM and STEM images determination of catalyst samples was\nacquired on the JEM-ARM200F STEM/TEM (resolution of 0.08 nm) and JEM-F200\ninstrument of JEOL, respectively. Sample was dispersed in EtOH and placed onto Cu\ngrids.\nThe CO pulse chemisorption experiment was carried out on the Zeton Altramira AMI-\n300 chemisorption instrument. About 100 mg samples were packed into a U-shaped\ntube using He as carrier gas at a flow rate of 30 mL min-1. The catalyst sample was first\nheated to 120 ℃ at a heating rate of 10 ℃ min-1 in a flow of He, purged for 1 h, and\ncooled to 50 ℃. Then, 10% CO/He mixture was quantitatively pulsing injected until\nadsorption saturation, and the released CO was detected by a TCD detector.”\n7) In Fig 2b, it demonstrated CO (not valeraldehyde) conversion. This might be written\nerror because the image is related the probe test of valeraldehyde hydrogenation.\nReply:\nWe are sorry for the mistake that has now been corrected in the revision.\nFig. 2. Compatibility assessment between syngas-to-oxygenates/olefins and the downstream\nhydroformylation or hydrogenation processes. (a) Catalyst performances between syngas-to-\noxygenates/olefins plus hydroformylation (left) and syngas-to-oxygenates/olefins plus\nhydrogenation (right). Reaction conditions: 210 °C (syngas-to-oxygenates/olefins) and 140 °C\n(hydroformylation/hydrogenation), H /CO = 1.5, 3.0 MPa, F = 65 ml min-1. (b) Catalytic\n2\nperformances of 5Pt/TiO and 5Pt4Sn/TiO for valeraldehyde hydrogenation in H and syngas\n2 2 2\nstreams. Reaction conditions: 5Pt/TiO or 5Pt4Sn/TiO , 1.5 g; T = 140 ℃; P = 3.0 MPa; F\n2 2\n(valeraldehyde) = 0.01 ml min-1; F (H ) or F (H /CO = 2) = 30 ml min-1. (c) WGS performances\n2 2\nand CO uptakes of CuZnAl, Cu/SiO , and CuZrO /SiO . Reaction conditions: catalysts 1.5 g; T =\n2 2 2\n140 ℃; P = 3.0 MPa; F (H O) = 0.01 ml min-1; F (CO) = 30 ml min-1. (d) Hexanal hydrogenation\n2\nand WGS reaction pathways on CuZrO model system.\n2\n8) From Table S6, it can be seen that the CO selectivity of Co Mn Cs/C|Rh /3v-\n2 0.5 0.1 1\nPOPs-PPh |CuZrO /SiO should show an upward trend with the increase of reaction\n3 2 2\ntemperature. Why is the CO selectivity at 230 ℃ lower than 220 ℃?\nThank you for your insightful question. We need to clarify that the temperature’s impact\non the performance of the tandem system was performed in a single test by ramping up\nthe temperature from 210 to 240 ℃. Besides, each of the original reported data were\ncollected after stabilization at the aimed temperatures for 24 h.\nOne can see that when the temperature was elevated from 210 to 220 ℃, the CO\nconversion significantly increased from 15% to 37%, accompanied with great\nfluctuations in the reaction system, which we suspect might result in higher CO\n2\nselectivity. In contrast, when the temperature was further increased from 220 to 230 °C,\nthe CO conversion slightly increased from 36.5% to 42.5%, while the system remained\nrelatively stable with milder impact on CO selectivity.\nfrom 210 to 220 ℃, we have repeated the set of experiments. In particular, we have\nperformed three consecutive samplings at 220 ℃ for a longer duration (Please kindly\nrefer to Table R3). One can see a higher initial CO conversion at 24 h. However, both\nthe CO conversion and product selectivity stabilized at comparable levels during 48-72\nh. Specifically, the CO selectivity stabilizes at approximately 4% which is about the\n2\nsame as the data at 230 ℃. We have now replaced the original 24 h data with the\nstabilized data at 72 h.\nTable R3. Influence of bed temperatures of the syngas-to-oxygenates/olefins reactor on the catalytic\nperformances of Co Mn Cs/C|Rh/3v-POPs-PPh |CuZrO /SiO tandem system for the syngas-to-\n0.5 0.1 3 2 2\nC alcohols conversion\n4+\nS / %\nT / ℃ X / %\nCO\nCH CO C C = aldehydes alcohols\n4 2 2+ 2+\n220-24 h 36.5 8.6 7.3 21.3 0.6 7.1 55.1\n220-48 h 33.2 4.8 4.2 20.5 1.3 5.4 63.8\n220-72 h 33.8 5.9 4.3 18.6 1.8 6.9 62.5\nReaction conditions: H /CO = 1.5, F = 130 ml min-1, 140 ℃ (hydroformylation/hydrogenation), and\n2\nSupplementary references\ntechnologies toward high-value commodities from syngas. Chin. J. Catal., 73, 16-28, (2025).\nhydroformylation over 3v-PPh polymer supported Rh catalysts. React. Kinet, Mech. Cat., 116, 223-\n3\n234, (2015).\n3\nhydroformylation of olefins. J. Mol. Catal. A, 404, 211-217, (2015).\n5 2\nalcohols. Nat. Commun. 11, 61, (2020).\nCatal. Today 281, 549-558, (2017).\nhydrogenation of carbon monoxide to higher alcohols. Nat. Commun. 14, 6808, (2023).\nconversion. J. Catal. 391, 446-458, (2020).\nover cesium-promoted Cu/ZnO/Al O Catalysts. ACS Catal. 6, 5771-5785, (2016).\n2 3\nactivity of Co/CuZnO for CO hydrogenation. J. Catal. 285, 208-215, (2012).\n3827, (2023).\nTropsch synthesis. Appl. Catal. A: Gen. 613, 118017, 118017 (2021).\n2\nalcohols and olefins from syngas. ACS Catal. 8, 228-241, (2017).\nx y\nalcohols: Effects of La promotion. J.. Catal. 361, 156-167, (2018).\ncarbon materials for direct synthesis of clean fuels by the addition of chromium. J. Catal. 370, 251-\n264, (2019).\nsyngas. Fuel 182, 42-49, (2016).\nx\nalcohols synthesis from syngas. Appl. Catal. B: Environ. 278, 119262, (2020).\ncatalysts: Influence of precursor activation. ACS Catal. 4, 2792-2800, (2014).\nSoc. 135, 7114-7117, (2013).\nselective CO hydrogenation to higher alcohols. ACS Catal. 5, 2929-2934, (2015).\naldehydes/alcohols and olefins/paraffins. Nat. Commun. 7, 13058, (2016).\nalcohols synthesis via syngas conversion. Appl. Catal.. B: Environ. 285, 119840, (2021).\nEnviron. 300, 120739 (2022).\noxidation pathways over natural mineral-inspired catalyst. Nat. Commun. 12, 6840, (2021).\nmultifunctional catalyst. Angew. Chem. Inter. Ed. 58, 4627-4631,(2019).\nFischer-Tropsch synthesis and reductive hydroformylation. Angew. Chem. Inter. Ed. 61,\ne202201004, (2022).\nstrategy on multifunctional relay catalysts. ACS Catal. 10, 2419-2430, (2020).\n2\nmultifunctional catalyst. ChenCatchem 13, 3184-3197, (2021).\n3\nhydroformylation: Chemical and DFT insights into Rh location and the roles of Xantphos and PPh .\nsite Rh-catalyzed heterogeneous hydroformylation. Nat. Commun. 15, 6967, (2024)."}, {"round": 2, "reviewer_comments": {"reviewer_2": "The authors have included extra information to support their results. The HRTEM images are particularly helpful.\nThe DFT calculations remain problematic.\nThe HRTEM image (Figure 1e) suggests Co2C islands are formed on metallic Co. The DFT model is the inverse: Co island on Co2C.\nRecent studies have conclusively shown that K is present as K2O during FT, and the O atoms play a crucial role in the promotion. The model with a single Cs atom (not Cs+) and the active site next to it is not representative for the actual sites.\nExperimental and modeling studies have shown that alkylidyne species are the key intermediates, not olefins.\nIf metallic Co sites are available, olefin hydrogenation will still dominate over CO insertion and olefin desorption, because of the much lower barrier.\nThe selectivity for Co/C is unusual. Experimental studies have shown that olefins are the primary products of Co-FT, the high selectivity to methane and oxygenates, and the high alkane/olefin ratio in Fig 1b should be compared to literature.\nThe grammar should be improved. Words are missing in some of the new sentences in the revised manuscript.", "reviewer_3": "In the revised manuscript, the authors well replied to the queries and made careful modification. So it may meet the publication requirements.", "reviewer_4": "I have reviewed the revised manuscript submitted by Li et al., along with the authors’ responses to the comments raised in the original round of peer review. Since I have joined the peer review process at this stage, I have taken into account both the content of the revised submission and the earlier reviewer remarks and authors' replies.\nThe authors present a dual-reactor, single-pass system for the conversion of syngas to higher alcohols. While the emphasis on C4+ alcohols rather than the more commonly targeted C2+ or C3+ alcohols is noted, I do not consider this shift in focus to represent a significant conceptual advance. Selectivity toward higher alcohols—except for ethanol, which cannot form via olefin hydroformylation—remains fundamentally constrained by the statistical nature of the Anderson–Schulz–Flory (ASF) product distribution. This is expected given that all alcohol products, either directly or indirectly, originate from FTS hydrocarbons formed on the surface of the first (Co-based) catalyst.\nIn several ways, this study appears as an extension of the authors’ earlier work (Li et al., ACS Catal. 2021, 11, 14791–14802; https://doi.org/10.1021/acscatal.1c04442), where a similar catalytic pairing, i.e., CoMn/AC for FTS and a Rh-based polymer catalyst for hydroformylation, was implemented within a single reactor using two packed-beds. In my opinion, the above article should have been cited in the current manuscript.\nThe primary distinctions in the present manuscript, relative to the earlier work are: (1) the addition of a third catalyst to hydrogenate aldehydes into alcohols, shifting the major oxygenate product class toward alcohols exclusively, and (2) the segmentation of the process into two reactors, allowing independent temperature control (210 °C for FTS and 140 °C for hydroformylation/hydrogenation), but clearly deviating form the concept of tandem operation of catalysts and reactions.\nThe experimental work in the current submission is thorough, optimizes there different catalysts (although with promoters which have been well described for the actual role they are meant for here) and the alcohol selectivities achieved are indeed notable, primarily due to the inhibition of C-O cleavage at the stage of hydroformylation and oxygenate hydroformylation thanks to splitting these conversion steps in another reactor operated at a milder temperature. Beyond the high selectivity, the claim of novelty appears somewhat overstated, especially with respect to the emphasis on C₄⁺ products. This emphasis, though presented as a point of differentiation, seems more arbitrary than chemically justified given the nature of the ASF product distribution. Thus, although the manuscript is compelling, and it deserves publication (following further revision), I do not perceive that the conceptual threshold typically required for a journal such as Nature Communications is reached.\nThe system described extends earlier work while increasing process complexity through the serial arrangement of two separate reactors. Referring to this as a “tandem” process is, in my view, inaccurate: chaining reactors without intermediate workup is standard industrial practice, particularly when distinct reaction conditions (e.g., temperature) are needed for sequential transformations.\nRegarding the authors’ responses to previous reviewer comments, all revision points have been addressed, but not all have been satisfactorily resolved in my opinion.\nIn response to requests for greater clarity in the DFT section, the authors have now provided full energetics along the calculated reaction pathways in tabulated form, which is appreciated. However, they have not included the coordinate files for the optimized models, as requested by the reviewers. This is important, particularly because concerns have been raised about the physical realism of the modeled surfaces. For instance, Cs on low work function metal surfaces like Co would be expected to adsorb as a neutral species (e.g., oxide or hydroxide) under FT conditions. The authors model Cs as a cation (Cs⁺), but no counterion is presented. I concur with other reviewers that this representation lacks chemical plausibility. Also, direct comparisons of energy profiles for fundamentally different reactions, such as the water–gas shift (WGS) and CO insertion into CₓHᵧ species, are overinterpretative without accompanying microkinetic modeling.\nThe reported methane selectivity (1.9–5.1 C%) appears unrealistically low to me, certainly falling below the ASF-predicted value. This is surprising, as the ASF value would be expected to be the theoretically lowest, even if hydrogenation activity, and hence overall conversion, has been heavily inhibited on a Co FTS catalyst. The authors should carefully re-examine their product quantification, include linearized ASF plots for all major product families, and assess the extent of any deviations from the expected statistical distribution. Selectivity trends across product classes are critically dependent on this analysis.\nAuthors should note that the comparison established in Figure 4b is very much dependent particularly on the CO/syngas conversion level at which selectivities are considered.\nOther, minor, comments are:\nThe authors attribute paraffin formation to excessive hydrogenation of oxygenates. However, complete hydrogenation of oxygenates should yield alcohols, not paraffins. If paraffins are indeed forming, C–O bond cleavage must be occurring, implying additional chemistries that have not been considered in the current discussion.\nThere is some inconsistency in the terminology used for catalyst preparation. The synthesis method is described at times as “incipient wetness impregnation” and at other times as “wetness impregnation.” These are distinct techniques, and the usage should be clarified to avoid confusion.\nThe miscorrespondence between the composition and the notation for the catalysts has not been solved upon revision, which makes it very hard for a reader to actually understand what the composition of each material discussed in the text is.\nFinally, the term “net CO₂ emissions” is typically associated with life-cycle analysis. Its use here to describe a scenario where minor CO₂ side-products are recycled upstream is, in my opinion, imprecise and should be revised."}, "author_response": "Nature Communications - Manuscript ID: NCOMMS-25-14503B\nResponse to Reviewers\nComments in blue - Replies in black - Actions in bold - Citations in italic\nReviewer #2 (Remarks to the Author):\nThe authors have included extra information to support their results. The HRTEM images are\nparticularly helpful.\nWe thank the Reviewer for recognizing our effort in this revision, and your further insightful\ncomments that are invaluable for improving the quality of this work.\nThe DFT calculations remain problematic. The HRTEM image (Figure 1e) suggests Co C islands\n2\nare formed on metallic Co. The DFT model is the inverse: Co island on Co2C.\nWe fully accept the criticism on the catalyst model that deviates from the characterization results.\nIn the initial modeling, the main objective was to establish the interface model between Co and\nCo C. We had two options, either building Co C on the top of Co nanoparticles (Co C-Co) or the\n2 2 2\ninversed model (Co-Co C). Considering that the former will lead to a much larger model, and\n2\nultimately needs longer calculation time, the inversed model of Co on top of Co C was selected for\n2\nthe modeling in the previous manuscript. To keep in line with the characterization data, we have\nnow switched back to the model of Co C on top of Co nanoparticles and completely replaced\n2\nin the revised manuscript (Figs. 1f, and S8-10, Table S3). It should be mentioned that, similar\ntrends were observed for the two selected models, thus hinting the critical role of Co and Co C\n2\ninterface structures in the syngas-to-oxygenates/olefins.\nRecent studies have conclusively shown that K is present as K2O during FT, and the O atoms play\na crucial role in the promotion. The model with a single Cs atom (not Cs+) and the active site next\nto it is not representative for the actual sites.\nThank you for the insightful comments that we fully agree. We have taken this into account when\nbinding the revised model for the CoMnCs/C catalyst. Specifically, in the new model, Cs\nspecies are placed at the interface between Co and Co C. We have updated the simulations of the\n2\nthree key fundamental steps, including desorption, hydrogenation, and carbon monoxide\ninsertion (Fig. 1f, Table S3 and S9-S10). \nExperimental and modeling studies have shown that alkylidyne species are the key intermediates,\nnot olefins. If metallic Co sites are available, olefin hydrogenation will still dominate over CO\ninsertion and olefin desorption, because of the much lower barrier.\nThe Reviewer is kindly reminded that it is C H *, but not alkylidyne, that C H * was adopted for\nn 2n 5 10\nthe modeling in our work. In fact, C H * has been widely used as the intermediate in syngas-to-\nn 2n\nalcohols synthesis in the previous studies (Appl. Phys. Rev., 2025, 12, 011311). “The metal cobalt\nfirst produces CH * through the adsorption of CO by dissociation and then promotes the formation\nx\nof C H * intermediates through a chain reaction. Due to the short distance between Co0 and Co C,\nn 2n 2\nC H * can quickly transfer from Co0 to Co Mo C. At the same time, Co Mo C assisted non-\nn 2n 6 6 6 6\ndissociative adsorption of CO to produce active CO*, which was inserted into adjacent C H *\nn 2n\nspecies to form acyl intermediate C H CO*, followed by hydrogenation to form the final\nn 2n\nC H OH alcohols.”\nn+1 2n+1\nRegarding the hydrogenation of olefins on metallic Co sites, this did not happen on the CoMnCs/C\ncatalyst likely due to its unique structure. At first, the Co and Co C interface structure inhibits the\n2\nhydrogenation of C H * to form alkanes, as confirmed by the DFT calculations. The results in Fig.\n5 10\n1f showed that the energy barriers of this step on Co(111) is significantly lower with 0.36 eV\ncompared to 1.62 eV on Co C-Co and 1.75 eV on Cs O-Co C-Co. Furthermore, Co nanoparticles\n2 2 2\nare in situ encapsulated by Co C, as evidenced by the detailed HRTEM analysis (Fig. R1). This\n2\ndistinct structure might also reduce the H adsorption capacity, thus inhibiting the further\n2\nhydrogenation of olefins.\n“The interfacial sites of Co C and Co nanoparticles, denoted hereafter as Co C-Co, are crucial for\n2 2\nthe preferential formation of alcohols33 34, and the addition of Cs can further enhance alcohol\nformation. Based on these observations and the catalyst characterization data, a new catalyst model\nof Cs O-Co C-Co, plus Co(111) and Co C-Co, was constructed to further elucidate their effects on\n2 2 2\nthe syngas-to-oxygenates/olefins activity and product distribution through DFT simulations (Fig.\nS8, Table S3). To explain the different product distributions, three key fundamental steps including\nthe desorption, hydrogenation, and CO insertion of C H * intermediates were simulated (Figs. 1f\n5 10\nand S9-S10). For Co(111), the energy barrier of *C H hydrogenation is lower than the desorption\n5 10\nenergy (0.36 vs. 0.63 eV). In contrast, the *C\n10\nintermediates are more prone to directly desorb to\n*C\n10\n(g) or undergo CO insertion instead of hydrogenation on Co\nsuggesting that Co C species can generally enhance the formations of olefins and oxygenates. The\n2\nenergy barrier differences between C H * hydrogenation and CO insertion were calculated and\n5 10\nused as a selectivity indicator. A larger difference was observed on Cs O-Co C-Co than on Co C-\n2 2 2\nCo (0.34 vs. 0.24 eV), explaining the improved selectivity towards oxygenates/olefins on the former.\nTo further understand the promotional effects of Cs addition on syngas-to-oxygenates/olefins\nactivity, we calculated the projected density of states (PDOS) for the different models (Fig. S11). It\nwas found that the 3d occupied and unoccupied electronic states of Co in Co(111) are significantly\nlocalized near the Fermi level. This indicated that the 3d electrons of Co are not easily engaged in\nstrong interactions with the 2p orbital electrons of the adsorbed CO, due to a mismatch in their\nenergy levels. In comparison to the Co C-Co model, the incorporation of Cs markedly broadens the\n2\ndistribution of Co's 3d orbitals, particularly promoting the extension of the 3d orbitals toward lower\nenergy levels. This effectively enhances the interaction between the C 2p and Co 3d orbitals,\nfacilitating CO activation as also supported by the Bader charge analysis (Fig. 1f).”\nFig. 1(f). The reaction coordinate of C H * desorption, hydrogenation, and CO insertion pathways.\n5 10\non Co(111), Co C-Co, and Cs O-Co C-Co models. Bader charge analysis results were shown in the\n2 2 2\ninsets.\nFig. S8. Illustrations of the top and side views of the surfaces of Co(111), Co C-Co, and Cs O-\n2 2\nCo C-Co.\n5 10\nCo C-Co, and Cs O-Co C-Co.\n2 2 2\nFig. S10. Illustrations of different configurations of *C H hydrogenation on the Co(111), Co C-\n5 10 2\nCo, and Cs O-Co C-Co.\n2 2\nTable S3. The detailed E, ∆H, T×∆S, ZPE, ∆G values for each IS, TS, and FS states of the reaction\npathway studied in different calculation models\nModel Adsorbate E / eV ZPE / eV ∆H / eV T·∆S / eV ∆G / eV\n*C H +*H -476.401 3.79037 4.29604 1.01725 3.27879\n5 10\nTS -474.539 3.7998 4.32034 1.089303 3.23104\nCo\n*C H +* -478.182 3.90762 4.423559 1.096589 3.32697\n5 11\n*C H +*H -481.493 4.09588 4.657957 1.214 3.443957\n5 11\nTS -481.256 4.17643 4.68669 1.107665 3.57902\n*C H +* -482.153 4.243895 4.72761 1.05287 3.67474\n5 12\n*C H +*CO -491.074 3.814761 4.439282 1.310257 3.129025\n5 10\nTS -489.132 3.78738 4.3921 1.29069 3.1015\n*C H CO -489.794 3.85222 4.44694 1.19525 3.25168\n5 10\n*C H +*H -973.421 3.770 4.281 1.028 3.253\n5 10\nTS -971.801 3.724 4.207 0.975 3.232\n*C H +* -973.118 3.900 4.382 0.989 3.393\n5 11\n*C H +*H -977.017 4.068 4.617 1.159 3.458\n5 11\nCo C-Co TS -976.347 4.087 4.616 1.102 3.514\n2\n*C H +* -976.889 4.235 4.713 1.011 3.702\n5 12\n*C H +*CO -985.857 3.761 4.406 1.344 3.063\n5 10\nTS -984.377 3.795 4.358 1.163 3.196\n*C H CO -984.695 3.877 4.481 1.287 3.194\n5 10\n*C H +*H -986.686 3.794 4.300 1.002 3.297\n5 10\nTS -984.936 3.706 4.144 0.887 3.257\n*C H +* -986.316 3.916 4.392 0.987 3.405\n5 11\n*C H +*H -990.443 4.089 4.629 1.129 3.500\n5 11\nCs O-\nCo C-Co\n2\n*C H +* -990.413 4.240 4.762 1.162 3.600\n5 12\n*C H +*CO -999.256 3.818 4.448 1.329 3.119\n5 10\nTS -997.746 3.803 4.375 1.171 3.204\n*C H CO -998.680 3.888 4.476 1.194 3.282\n5 10\n*H O -434.871 0.622854 0.744382 0.269046 0.475336\n*OH+*H -434.788 0.521215 0.624136 0.172818 0.451318\n*CO+*OH+*H -450.507 0.698897 0.922948 0.420045 0.502903\nTS -449.488 0.711526 0.900765 0.396387 0.504378\n*COOH+*H -450.148 0.772586 0.968776 0.421367 0.547409\nTS -449.075 0.587511 0.734066 0.294878 0.439187\n*CO +*H -449.383 0.591737 0.761651 0.35426 0.407389\n2 2\n*H -427.223 0.294778 0.410038 0.280709 0.129328\n*2H -427.769 0.350252 0.37815 0.036417 0.341733\n*C H CHO+*H -529.36 4.661801 5.155494 1.065767 4.089727\n5 11\nTS -527.71 4.618257 5.08528 0.955278 4.130002\n*C H CH O+* -528.93 4.764797 5.170733 0.800561 4.370172\n5 11 2\n*C H CH O+*H -532.276 4.9056 5.351431 0.91401 4.43742\n5 11 2\nTS -532.106 4.87405 5.357289 0.99015 4.367139\n*C H CH OH+* -533.395 5.117547 5.586337 0.96158 4.624758\n5 11 2\n*H O -1744.2 0.634097 0.773856 0.318171 0.455685\n*OH+*H -1744.29 0.479353 0.58429 0.2266 0.35769\n*CO+*OH+*H -1757.15 0.53155 0.71298 0.357041 0.35594\nTS -1756.09 0.568742 0.728394 0.31864 0.409753\n*COOH+*H -1759.48 0.718562 0.860856 0.292235 0.568621\nTS -1758.98 0.627312 0.768796 0.289707 0.479089\n*CO +*H -1759.39 0.659887 0.813417 0.284827 0.52859\n2 2\n*H -1736.3 0.305213 0.373511 0.129036 0.244476\n2\n*2H -1737.26 0.337568 0.379741 0.064128 0.315613\n*C H CHO+*H -1839.46 4.650485 5.047186 0.777926 4.26926\n5 11\nTS -1838.82 4.618898 5.04363 0.872195 4.171435\n*C H CH O+* -1839.38 4.786809 5.199093 0.85693 4.342163\n5 11 2\n*C H CH O+*H -1842.54 4.970997 5.416286 0.913088 4.503198\n5 11 2\nTS -1842.08 4.931647 5.352619 0.848944 4.503675\n*C H CH OH+* -1843.15 5.147832 5.560021 0.828798 4.731223\n5 11 2\nThe selectivity for Co/C is unusual. Experimental studies have shown that olefins are the primary\nproducts of Co-FT, the high selectivity to methane and oxygenates, and the high alkane/olefin ratio\nin Fig 1b should be compared to literature.\nThank you for the very relevant comments. We have supplemented an additional table (Table S2)\nto compare these important data with those from the previous works in the Supplementary\nInformation. We have also added relevant comments in the revised piece: “In particular,\nCo Mn Cs/C exhibited lower alkanes/olefins ratios（0.7-0.9） and the highest total selectivity\n0.5 0.1\nof oxygenates/olefins, with the total selectivity of C oxygenates/C olefins reaching 73% (Tables\n4+ 3+\nS2).”\nTable S2. Catalytic performances of various catalysts for syngas conversion to oxygenates in the\nliteratures.\nS / %\nGHSV T / X Alk/Ole\nCatalysts H /CO CO Refs.\n/ h-1 2 oC / % / %\nCO Alk Ole Oxy\nCo Cs/C 2000 2.0 210 11.7 2.1 32.3 36.4 29.2 0.9 TW\n0.1\nCo Mn/C 2000 2.0 210 20.0 0.6 39.6 35.8 24.0 1.1 TW\n0.5\nCo Mn/C 2000 2.0 210 18.9 1.0 37.9 41.0 20.2 0.9 TW\n0.5 0.1\nCo Mn Cs/C 2000 1.5 210 25.5 2.6 26.1 37.6 33.6 0.7 TW\n0.5 0.1\nCo Mn Cs/C 4000 1.5 210 12.4 0.6 22.2 30.4 46.4 0.7 TW\n0.5 0.1\nCo Cu 7200a 1.5 240 11.0 1.0 53.2 15.0 30.8 3.5 1\n4 1\nCo Cu 2000 2 240 5.0 12.0 35.0 25.0 28.0 1.4 2\n1 1\nCo Cu Nb 40b 1.5 200 6.0 1.3 28.3 18.4 52.0 1.5 3\n1 2 0.2\nCo Cu Mn 2000 2 240 18.0 8.0 34.0 24.0 34.0 1.4 2\n1 1 1\nCo Mn K 40b 1.5 220 18.0 16.0 24.0 20.0 38.0 1.2 4\n4 1 0.1\n0.3Rh-CoMn 2000a 1 220 29.5 20.4 24.6 26.7 28.3 0.9 6\n0.3Ru-CoMn 2000a 1 220 32.6 23.3 33.7 20.0 22.9 1.7 6\nCo/MnOx@quasi-\n4500a 2 230 21.4 0.8 38.6 21.6 35.9 1.8 7\nMOF-74\na ml gcat −1 h−1. b ml min−1.\nThe grammar should be improved. Words are missing in some of the new sentences in the revised\nmanuscript.\nWe are sorry for the mistakes and have carefully checked and corrected these.\n“Syngas-to-oxygenates/olefins are is the key step to produce C long-chain alcohols”\n4+\n“This was further supported by line-scanning of an individual nanoparticle, showing relatively even\ndistributions of Cs and Mn across the nanoparticles but much higher C signal than that of Co at the\nperiphery (Fig. 1d).”\n“Two porous organic polymers (POPs)-supported single-Rh-site Rh catalysts”\n“Secondly, water-gas shift (WGS) reaction on different Cu catalysts were was studied.”\nReviewer #3 (Remarks to the Author):\nIn the revised manuscript, the authors well replied to the queries and made careful modification. So\nit may meet the publication requirements.\nWe are grateful for your support of the publication of our work.\nReviewer #4 (Remarks to the Author):\nI have reviewed the revised manuscript submitted by Li et al., along with the authors’ responses to\nthe comments raised in the original round of peer review. Since I have joined the peer review process\nat this stage, I have taken into account both the content of the revised submission and the earlier\nreviewer remarks and authors' replies.\nWe warmly thanked the Reviewer for his/her careful reading and the insightful comments and\nguidance on our manuscript.\nThe authors present a dual-reactor, single-pass system for the conversion of syngas to higher\nalcohols. While the emphasis on C alcohols rather than the more commonly targeted C2+ or C3+\n4+\nalcohols is noted, I do not consider this shift in focus to represent a significant conceptual advance.\nSelectivity toward higher alcohols-except for ethanol, which cannot form via olefin\nhydroformylation-remains fundamentally constrained by the statistical nature of the Anderson–\nSchulz-Flory (ASF) product distribution. This is expected given that all alcohol products, either\ndirectly or indirectly, originate from FTS hydrocarbons formed on the surface of the first (Co-based)\ncatalyst.\nWe sincerely thank the Reviewer for this important point. We fully agree that product selectivity in\nsyngas-to-oxygenates/olefins is generally constrained by the ASF distribution. Nevertheless, we\nwould like to emphasize high selectivity of C alcohol. Ethanol and propanol are common\n4+\nchemicals, whereas C alcohols are used in fine chemicals. The reason why we chose C alcohol\n4+ 4+\nselectivity as indicator is that butanol can be directly used as the lowest carbon number of plasticizer\nalcohol, offering significant economic advantages.\nIn this integrated system, a large fraction of straight-chain α-alcohols is directly produced over the\nCs O-Co C-Co active site, whereas the additional alcohols originate from the hydroformylation of\n2 2\nby-product olefins. The overall n/i (normal and isomeric alcohols) ratio of the system is between 4\nand 5 (Table S4). In the revised manuscript, we have incorporated the Anderson–Schulz–Flory (ASF)\nproduct distribution. In the integrated system, the C –C products deviate from the ASF linear\n1 3\ndistribution, and the chain growth probability α increases from 0.65 to 0.68, indicating that the\nhydroformylation process effectively modulates product distribution.\nWe believe this represents a meaningful advance, even within the ASF constraint, as current reports\ntypically achieve <45% C oxygenates selectivity (Table S5).\n4+\nFig. S3. Products chain lengthening. Detailed selectivity patterns and Anderson-Schulz-Flory\n(ASF) chain-lengthening characteristics of the various product classes over (a) Co Cs/C, (b)\n0.1\nCo Mn/C, (c) Co Mn Cs/C, (d) integrated system.\n0.5 0.5 0.1\nIn several ways, this study appears as an extension of the authors’ earlier work (Li et al., ACS Catal.\n2021, 11, 14791–14802; https://doi.org/10.1021/acscatal.1c04442), where a similar catalytic pairing,\ni.e., CoMn/AC for FTS and a Rh-based polymer catalyst for hydroformylation, was implemented\nwithin a single reactor using two packed-beds. In my opinion, the above article should have been\ncited in the current manuscript.\nWe thank the Reviewer for drawing attention to this point. The data of our previous work (ACS\nCatal. 2021, 11, 14791–14802) was already included in Fig. 3e for the comparison, and has now\nbeen clearly cited in the revised manuscript (Fig. 3e and Table S5). Comparisons and references\nwere also made in the manuscript, “Tandem catalysis approaches have achieved improved results,\nwith notable results including CoMn|CuZnAlZr (46% oxygenates selectivity)25, CuCoAl|t-ZrO (33%\n2+ 2 2+ x\n(60% total alcohol selectivity)28, CoMn/MAC(P)|Rh/3v-PPh @POPs (60.8% total oxygenates\n3\nselectivity)29 and NaPr-CoRu/AomM|Co CO + PCy (54% total alcohol)30.”\n2 8 3\nWe also highlight the key differences: in the earlier work, the C oxygenates selectivity plateaued\n4+\nat ~45% (Table S5), whereas in the present study, by rationally regulating the reaction network,\nprecisely constructing the syngas-to-oxygenates/olefins catalyst (Cs O-Co C-Co) to direct control\n2 2\nkey the steps, and subsequently integrating the hydroformylation and hydrogenation systems to\ntailored specific pathways, an outstanding C + alcohol selectivity of 80% was achieved. Thus,\n4\nalthough our study builds upon prior work, the catalyst design and process segmentation here enable\na significant breakthrough for syngas to C alcohol with higher selectivity.\n4+\nThe primary distinctions in the present manuscript, relative to the earlier work are: (1) the addition\nof a third catalyst to hydrogenate aldehydes into alcohols, shifting the major oxygenate product class\ntoward alcohols exclusively, and (2) the segmentation of the process into two reactors, allowing\nindependent temperature control (210 °C for FTS and 140 °C for hydroformylation/hydrogenation),\nbut clearly deviating form the concept of tandem operation of catalysts and reactions.\nWe appreciate the Reviewer’s thoughtful assessment. Agree with the reviewer's opinion and make\ncorresponding modification in advised manuscript. The following actions have been made in the\nrevision:\n(i) We have revised the manuscript text (please kindly refer to the Discussion section, or the\nanswers to your next question) to more cautiously present these advances and to clarify that\nour innovation lies in the precise integration and adaptation of three different catalytic steps,\nrather than in redefining the concept of “tandem catalysis.”\n(ii) We have replaced the term “tandem” with “integrated” throughout the revision.\nThe experimental work in the current submission is thorough, optimizes there different catalysts\n(although with promoters which have been well described for the actual role they are meant for here)\nand the alcohol selectivities achieved are indeed notable, primarily due to the inhibition of C-O\ncleavage at the stage of hydroformylation and oxygenate hydroformylation thanks to splitting these\nconversion steps in another reactor operated at a milder temperature. Beyond the high selectivity,\nthe claim of novelty appears somewhat overstated, especially with respect to the emphasis on C₄⁺\nproducts. This emphasis, though presented as a point of differentiation, seems more arbitrary than\nchemically justified given the nature of the ASF product distribution. Thus, although the manuscript\nis compelling, and it deserves publication (following further revision), I do not perceive that the\nconceptual threshold typically required for a journal such as Nature Communications is reached.\nWe sincerely thank the Reviewer for the careful evaluation and for recognizing the thoroughness of\nour experimental work, the design of catalysts, and the notable alcohol selectivity achieved. The\nreviewer's judgment that the C-O cleavage at slight high reaction temperature (for example, lower\nthan 200 oC in hydroformylation leads to the reduction of alcohols selectivity is not agreed. In fact,\nunder the present reaction conditions, increasing temperature primarily enhances the hydrogenation\nof olefins rather than promoting C-O cleavage, which generally requires significantly harsher\nconditions.\nWe also acknowledge the Reviewer’s concern that our emphasis on C alcohols could appear\n4+\noverstated, since the ASF product distribution intrinsically governs chain growth probabilities. In\nthe revised manuscript, we have therefore moderated our claims and clarified that the novelty\nof our work does not solely lie in the focus on C products.\n4+\nSyngas-to-long-chain alcohols involves a complex reaction network. In the work, by precisely\nconstructing a Cs O-Co C-Co active-center structure, achieving the highly selective generation of\n2 2\noxygenates and olefins in one step. Subsequently, by designing hydroformylation catalysts and\nanti-CO poisoning aldehydes hydrogenation catalysts under identical reaction conditions\ncapable of effectively suppressing side reactions—such as the water-gas shift and methanation\nreactions—we have constructed a directionality and synergistically coupled reaction channels,\nthereby facilitating the selective synthesis of C alcohols. This study successfully resolves the\n4+\ncatalyst compatibility issue and enables efficient cooperation among catalytic units within the\nmultifunctional integrated system, representing a key advancement.\nIn the revised manuscript, we have carefully rephrased our novelty claims in Abstract and\nDiscussion section to more accurately reflect these advances and to avoid overstatement. We\ngreatly appreciate the Reviewer’s constructive guidance, which has helped us present a more\nbalanced and rigorous account of our work.\nAbstract\nThe selective conversion of syngas to C long-chain alcohols holds significant industrial and\n4+\nscientific interest, but challenges in product selectivity and process efficiency remain. Here, we\nreport a precisely integration integrated catalytic strategy for C alcohol synthesis with a record-\n4+\nbreaking selectivity of 80% at 17% CO conversion. The reaction channel involves: (i) the\ndevelopment of Cs O-Co C-Co catalysts capable of catalyzing CO hydrogenation to long-chain\n2 2\noxygenates/olefins; and (ii) subsequent complete conversion to C alcohols on the single-Rh-site\n4+\nand Cu-ZrO interfaces by tandem integrated cooperative catalysis. Comprehensive catalyst design\n2\nand compatibility assessment of each catalytic module ensure optimal combinations for cooperative\ncatalysis, meanwhile effectively eliminates costly separation steps, and reduces CO selectivity\n2\ndown to 1%. The developed process achieves ultra-high carbon-efficiency (>95%) and improves\noxygen-efficiency, effectively overcoming the key limitations of current syngas conversion\ntechnologies and thus representing a competitive and sustainable solution for producing high-value\nlong-chain alcohols with a minimal carbon footprint.\nDiscussion\nThe novel catalysis catalytic system presented in this study marks a significant breakthrough\ndemonstrates a meaningful advance in the conversion of syngas to C long-chain higher alcohols.\n4+\nThe results show that careful catalyst design and process integration can substantially shift the\nproduct distribution toward C₄⁺ long-chain alcohols by precise control of the reaction channels. The\nsystem achieves an unprecedented selectivity of 80% C long-chain alcohols with a remarkably\n4+\nlow CO selectivity of 1% and 17% CO conversion uUnder optimized conditions of (H /CO = 1.5,\n2 2\nF = 130 ml min-1, 210 oC for syngas-to-oxygenates/olefins, 140 oC for\nhydroformylation/hydrogenation), the system achieved up to 80% selectivity to C₄⁺ alcohols with\nonly 1% CO₂ selectivity, 17% CO conversion, and has ultra-high 97% overall carbon efficiency. and\nimproved oxygen-efficiency, effectively addressing a key limitation of the current syngas\nconversion technologies. The in situ reconstructed Cs₂O-Co₂C-Co active sites play a crucial role in\ndirecting the steps and intermediates toward oxygenates/olefins. Cs modification enhances Co\ndispersion favoring olefin desorption and CO insertion. In the subsequent stages by precisely\nregulating the reaction channels, single-site Rh catalysts enable efficient olefin-to-aldehyde\nconversion while suppressing overhydrogenation, and CuZrO₂/SiO₂ catalysts effectively\nhydrogenate aldehydes under syngas conditions, mitigating CO poisoning and minimizing side\nreactions. The stable CoCs@Co C active sites reconstructed in situ play a pivotal role in steering\n2\nthe reaction toward desired intermediates, particularly oxygenates/olefins. Cs-modification of\nCoCs@Co C active sites reduce the olefin desorption barrier and facilitate CO insertion, promoting\n2\nthe formation of oxygenates/olefins. In the second stage, single-Rh-site catalysts ensure the efficient\nolefin-to-aldehyde conversion while avoiding over-hydrogenation to alkanes. Subsequently,\nCuZrO /SiO catalysts effectively hydrogenate aldehydes under syngas conditions, preventing CO\n2 2\npoisoning and minimizing side reactions, thereby achieving high alcohol selectivity with excellent\nstability. The strategic cooperative catalysis illustrates how rationally matching three distinct\ncatalytic modules under temperature optimized conditions can achieve both high alcohol selectivity\nand operational stability. Rather than representing a complete departure from ASF-type behavior,\nthis work provides a practical pathway to enhanced higher-alcohol selectivity through precise\nactive-site engineering, staged reactor operation, and catalyst compatibility. We believe these\nfindings offer valuable guidance for designing integrated catalytic systems for the sustainable and\nscalable production of long-chain alcohols from syngas. between different modules enables efficient\nand direct syngas-to-C alcohol synthesis with greatly reduced reaction and separation units,\n4+\nthereby, it represents a transformative advance in syngas conversion, offering a competitive and\nimpactful solution for sustainable, scalable, and economically viable production of value-added\nlong-chain alcohols.\nThe system described extends earlier work while increasing process complexity through the serial\narrangement of two separate reactors. Referring to this as a “tandem” process is, in my view,\ninaccurate: chaining reactors without intermediate workup is standard industrial practice,\nparticularly when distinct reaction conditions (e.g., temperature) are needed for sequential\ntransformations.\nWe appreciate the Reviewer’s thoughtful assessment. Agree with the reviewer's opinion and make\ncorresponding modification in advised manuscript.\nWe thank the Reviewer again for this clarification. We agree that, strictly speaking, connecting\nreactors in series is an industrial practice rather than “tandem catalysis” in the conventional sense.\nTo avoid confusion, we have avoided to use the term “tandem” when describing our approach.\nAt the same time, we emphasize that the challenge addressed here lies not in the serial connection\nitself, but in achieving effective compatibility of three distinct catalysts and reaction conditions. In\naddition, the lower-temperature bed benefits from the residual heat of the upstream reactor,\ncontributing to process efficiency. We have clarified these points in the revised text. We have\nreplaced the term “tandem” with “integrated” throughout the revision.\nRegarding the authors’ responses to previous reviewer comments, all revision points have been\naddressed, but not all have been satisfactorily resolved in my opinion.\n(1) In response to requests for greater clarity in the DFT section, the authors have now provided\nfull energetics along the calculated reaction pathways in tabulated form, which is appreciated.\nHowever, they have not included the coordinate files for the optimized models, as requested\nby the reviewers. This is important, particularly because concerns have been raised about the\nphysical realism of the modeled surfaces.\nThank you for the critical comments. We have adopted the reviewers' suggestions and\nincluded the coordination file of the optimized model in the revised manuscript.\n(Supplementary document for details).\nFor instance, Cs on low work function metal surfaces like Co would be expected to adsorb as\na neutral species (e.g., oxide or hydroxide) under FT conditions. The authors model Cs as a\ncation (Cs⁺), but no counterion is presented. I concur with other reviewers that this\nrepresentation lacks chemical plausibility.\nWe agree with the Reviewer and have replaced Cs with Cs O in the catalyst model in the\n2\nrevision. The new calculation data have been provided in Figs. 1f and S8-10.\n(2) Also, direct comparisons of energy profiles for fundamentally different reactions, such as the\nwater–gas shift (WGS) and CO insertion into CₓHᵧ species, are overinterpretative without\naccompanying microkinetic modeling.\nWe sincerely thank the Reviewer for this constructive comment. We fully agree that direct\ncomparisons of energy barriers between fundamentally different reactions, such as the WGS\nand hydrogenation steps, are not rigorous without microkinetic modeling. In the revised\nmanuscript, we have removed such fundamentally different reaction comparisons and now\nonly present the energy barriers for valeraldehyde hydrogenation on Cu(111) and CuZrO\n2\nmodels (Fig. 2d). This revision avoids potential overinterpretation. We greatly appreciate this\nvaluable suggestion and will pursue microkinetic modeling in our future work to enable more\naccurate comparisons.\nFig. 1(f). The reaction coordinate of C H * desorption, hydrogenation, and CO insertion pathways.\n5 10\nFig. S8. Illustrations of the top and side views of the surface of Co(111), Co C-Co, and Cs O-Co C-\n2 2 2\nCo.\nFig. S9. Illustrations of different configurations of *CO insertion into *C H species on the Co(111),\n5 10\nCo C-Co, and Cs O-Co C-Co.\n2 2 2\nFig. S10. Illustrations of different configurations of *C H hydrogenation on the Co(111), Co C-\n5 10 2\nCo and Cs O-Co C-Co.\n2 2\nTable S3. The detailed E, ∆H, T×∆S, ZPE, ∆G values for each IS, TS, and FS states of the reaction\npathway studied in different calculation models\nModel Adsorbate E / eV ZPE / eV ∆H / eV T·∆S / eV ∆G / eV\n*C H +*H -476.401 3.79037 4.29604 1.01725 3.27879\n5 10\nTS -474.539 3.7998 4.32034 1.089303 3.23104\n*C H +* -478.182 3.90762 4.423559 1.096589 3.32697\n5 11\nCo\n*C H +*H -481.493 4.09588 4.657957 1.214 3.443957\n5 11\nTS -481.256 4.17643 4.68669 1.107665 3.57902\n*C H +* -482.153 4.243895 4.72761 1.05287 3.67474\n5 12\n*C H +*CO -491.074 3.814761 4.439282 1.310257 3.129025\n5 10\nTS -489.132 3.78738 4.3921 1.29069 3.1015\n*C H CO -489.794 3.85222 4.44694 1.19525 3.25168\n5 10\n*C H +*H -973.421 3.770 4.281 1.028 3.253\n5 10\nTS -971.801 3.724 4.207 0.975 3.232\n*C H +* -973.118 3.900 4.382 0.989 3.393\n5 11\n*C H +*H -977.017 4.068 4.617 1.159 3.458\n5 11\nCo C-Co TS -976.347 4.087 4.616 1.102 3.514\n2\n*C H +* -976.889 4.235 4.713 1.011 3.702\n5 12\n*C H +*CO -985.857 3.761 4.406 1.344 3.063\n5 10\nTS -984.377 3.795 4.358 1.163 3.196\n*C H CO -984.695 3.877 4.481 1.287 3.194\n5 10\n*C H +*H -986.686 3.794 4.300 1.002 3.297\n5 10\nTS -984.936 3.706 4.144 0.887 3.257\n*C H +* -986.316 3.916 4.392 0.987 3.405\n5 11\n*C H +*H -990.443 4.089 4.629 1.129 3.500\n5 11\nCs O-\nCo C-Co\n2\n*C H +* -990.413 4.240 4.762 1.162 3.600\n5 12\n*C H +*CO -999.256 3.818 4.448 1.329 3.119\n5 10\nTS -997.746 3.803 4.375 1.171 3.204\n*C H CO -998.680 3.888 4.476 1.194 3.282\n5 10\n*H O -434.871 0.622854 0.744382 0.269046 0.475336\n*OH+*H -434.788 0.521215 0.624136 0.172818 0.451318\n*CO+*OH+*H -450.507 0.698897 0.922948 0.420045 0.502903\nTS -449.488 0.711526 0.900765 0.396387 0.504378\n*COOH+*H -450.148 0.772586 0.968776 0.421367 0.547409\nTS -449.075 0.587511 0.734066 0.294878 0.439187\n*CO +*H -449.383 0.591737 0.761651 0.35426 0.407389\n2 2\n*H -427.223 0.294778 0.410038 0.280709 0.129328\n*2H -427.769 0.350252 0.37815 0.036417 0.341733\n*C H CHO+*H -529.36 4.661801 5.155494 1.065767 4.089727\n5 11\nTS -527.71 4.618257 5.08528 0.955278 4.130002\n*C H CH O+* -528.93 4.764797 5.170733 0.800561 4.370172\n5 11 2\n*C H CH O+*H -532.276 4.9056 5.351431 0.91401 4.43742\n5 11 2\nTS -532.106 4.87405 5.357289 0.99015 4.367139\n*C H CH OH+* -533.395 5.117547 5.586337 0.96158 4.624758\n5 11 2\n*H O -1744.2 0.634097 0.773856 0.318171 0.455685\n*OH+*H -1744.29 0.479353 0.58429 0.2266 0.35769\n*CO+*OH+*H -1757.15 0.53155 0.71298 0.357041 0.35594\nTS -1756.09 0.568742 0.728394 0.31864 0.409753\n*COOH+*H -1759.48 0.718562 0.860856 0.292235 0.568621\nTS -1758.98 0.627312 0.768796 0.289707 0.479089\n*CO +*H -1759.39 0.659887 0.813417 0.284827 0.52859\n2 2\n*H -1736.3 0.305213 0.373511 0.129036 0.244476\n2\n*2H -1737.26 0.337568 0.379741 0.064128 0.315613\n*C H CHO+*H -1839.46 4.650485 5.047186 0.777926 4.26926\n5 11\nTS -1838.82 4.618898 5.04363 0.872195 4.171435\n*C H CH O+* -1839.38 4.786809 5.199093 0.85693 4.342163\n5 11 2\n*C H CH O+*H -1842.54 4.970997 5.416286 0.913088 4.503198\n5 11 2\nTS -1842.08 4.931647 5.352619 0.848944 4.503675\n*C H CH OH+* -1843.15 5.147832 5.560021 0.828798 4.731223\n5 11 2\nFig. 2(d). Valeraldehyde hydrogenation reaction on Cu(111) and CuZrO model system.\nbelow the ASF-predicted value. This is surprising, as the ASF value would be expected to be the\ntheoretically lowest, even if hydrogenation activity, and hence overall conversion, has been heavily\ninhibited on a Co FTS catalyst. The authors should carefully re-examine their product quantification,\ninclude linearized ASF plots for all major product families, and assess the extent of any deviations\nfrom the expected statistical distribution. Selectivity trends across product classes are critically\ndependent on this analysis.\nWe are extremely grateful for the insightful comments from the Reviewer. We have supplemented\nthe ASF distribution of syngas-to-oxygenates/olefins and integrated system (Fig. S3). H and\nto produce methane and other alkanes (Table R1). This also explains the presence of significant\nolefin content in the product, which is slightly lower than the methane value predicted by ASF\nVe\n/\nygrene\nevitaleR\nC H5\nC\nC H C\n5 11\n0 .5\nC H O + H\n11 2\nTS\nH C H O *+ H * 5 11 2\nC H C 5 11\nRe\nH\nH\na\nO H y d\nO *+ 2 H *\nc t io n\nro g e n a tio n P a th s\nC\nC\nTS\nTS\nC H C H O *+ H * 5 11 2\nC H5\ncoordinat e/ -\nu Z rO\n2\nu (1 1 1 )\nC H C H 5 11\nC H O H\n11 2\nO2\n*\nH\ndistribution. The CH selectivity of the integrated system at 210 oC was 6.6%, and the ASF\n4\ndistribution also conformed to expectations. In addition, low H /CO ratio is another reason for the\n2\nlow methane selectivity. In the manuscript, at a lower H /CO ratio of 0.5, the conversion rate is low\n2\nand the methane selectivity was 1.9% (Table S7). At low reaction rates, the C -C products will\n1 3\ndeviate from the linear ASF distribution, which is a common phenomenon in Fischer-Tropsch\nsynthesis as reported in previous references (Nat. Commun. 2019, 10, 3953): “However, significant\ndeviations from the linear ASF behavior are seen for C–C on the low rate branch. These deviations\n1 3\nseem to be general.”.\nTable R1. H and CO chemisorption characterization data for CoMnCs/C samples.\n2 cat cat\nCoMnCs/C 7.2 69.4\nTable S7. Influence of H /CO ratios on the catalytic performances of Co Mn Cs/C|Rh/3v-POPs-\n2 0.5 0.1\nPPh |CuZrO /SiO tandem system for the syngas-to-C alcohols conversion.\n3 2 2 4+\nH /CO S / %\nCO\nmol mol-1 CH CO C C = aldehydes alcohols\n4 2 2+ 2+\n1/2 3.7 1.9 3.1 9.9 1.4 1.4 82.2\nFig. S3. Products chain lengthening. Detailed selectivity patterns and Anderson-Schulz-Flory\n(ASF) chain-lengthening characteristics of the various product classes over (a) Co Cs/C, (b)\n0.1\nCo Mn/C, (c) Co Mn Cs/C, (d) integrated system.\n0.5 0.5 0.1\nAuthors should note that the comparison established in Figure 4b is very much dependent\nparticularly on the CO/syngas conversion level at which selectivities are considered.\nWe sincerely thank the Reviewer for this insightful comment. We fully acknowledge that product\nselectivity is strongly dependent on the CO/syngas conversion level. In Fig. 4b, our intention was\nto provide a comparative overview of the selectivity toward target products (C higher alcohols,\n4+\nC higher oxygenates, and C olefins) obtained from syngas by different pathways reported in the\n4+ 3+\nliterature. As these pathways employ distinct catalysts (Co-, Fe-, and Mo-based), and operate under\nmarkedly different conditions (reaction temperature, pressure, H /CO ratio, etc.), with\n2\ncorrespondingly different mechanisms and elementary steps, a direct comparison under identical\nconversion levels was not feasible (only three reference catalysts with comparable conversions were\navailable in the literature). For completeness, the detailed catalytic performance, including\nconversion and selectivity data from the cited references, has now been summarized in Table\nS5. Furthermore, we have revised Fig. 4b to improve the clarity.\n4+\n60\n40\n20\n0\n0 10 20 30 40 50 60\nFig. 4(b). Comparison on the C alcohol and CO selectivity from different technologies. (red, C\n4+ 2 4+\nalcohols synthesis Route: C alcohols selectivity, 1.CoMnCs/C|Rh /3v-POPs-PPh |CuZrO /SiO , 2.\n4+ 1 3 2 2\nCoMnCs/MC|Rh /POPs-BP&PPh |CuZrO /SiO ; black, Route 1: C olefins selectivity, 3.Mn-χ-\n1 3 2 2 3+\nFe C 44, 4.FeMn@Si 45, 5.χ-Fe C 44, 6.1.5Na-Fe Zn 46, 7.Fe-Al O (SCS350) 47, 8.Na S-Fe-CNF\n5 2 5 2 1 1 2 3 2\n44, 9.Fe-Al O (SCP) 47, 10.Fe O /MAG 48; blue, Route 2: C oxygenates selectivity,\n2 3 3 4 4+\n11.Co/MnO @quasi-MOF-7449, 12.CoMn|CuZnAlZr 25, 13.Co Mn K 50,14.ZnCrAlO |KNiMoS-\nx 4 1 0.1 x\nMMO-5 28, 15.Cu Fe Mg -MMO 20, 16.ER-MoS -K 51. See Supplementary Table S5 for more\n4 1 4 2\ndetails).\nOther, minor, comments are:\nThe authors attribute paraffin formation to excessive hydrogenation of oxygenates. However,\ncomplete hydrogenation of oxygenates should yield alcohols, not paraffins. If paraffins are indeed\nforming, C-O bond cleavage must be occurring, implying additional chemistries that have not been\nconsidered in the current discussion.\nThank you for your insightful comments. To more clearly express our current viewpoint, we have\nrevised this part to more clearly elaborate on this point. “In addition to the poisoning effect of\nCO on hydrogenation catalysts, other side reactions could occur including generations of CH and\n4\nmethanol, and water-gas shift reaction, and excessive hydrogenation of oxygen-containing\ncompounds to alkanes.”\nThere is some inconsistency in the terminology used for catalyst preparation. The synthesis method\nis described at times as “incipient wetness impregnation” and at other times as “wetness\nimpregnation.” These are distinct techniques, and the usage should be clarified to avoid confusion.\nThe miscorrespondence between the composition and the notation for the catalysts has not been\nsolved upon revision, which makes it very hard for a reader to actually understand what the\ncomposition of each material discussed in the text is.\nThank you for pointing out the inconsistency. We have revised the expressions to \"incipient\n%\n/ ytivitceleS\ntcudorP\n4+ Route 1 to C olefins\n3+\n2\n3\n12 13 4 6 8\n5\n10 11 9\n15\n14 7\n16\nwetness impregnation\". “The modified Co/C catalysts were prepared by incipient wetness\nimpregnation method.”\nTable S12. Synthetic approach and compositions of different catalysts in this work\nSynthesis Elements of Nominal Measured\nCatalyst\nmethod composition Content / wt% content / wt%\nincipient\nCo/C wetness Co 15 15.2\nimpregnation\nincipient Co 15 14.9\nCo Mn/C wetness\n0.5\nMn 0.5 0.5\nimpregnation\nincipient Co 15 15.1\nCo Cs/C wetness\n0.1\nCs 0.1 0.1\nimpregnation\nincipient Co 15 14.9\nCo Mn Cs/C wetness Mn 0.5 0.5\n0.5 0.1\nimpregnation Cs 0.1 0.1\nRh/3v-POPs-PPh post-loading Rh 0.125 0.1\n3\nammonia Cu 20 19.0\nCuZrO /SiO\n2 2\nevaporation Zr - 28.0\nammonia\nCu/SiO Cu 20 22.0\n2\nevaporation\na Determined from ICP-OES.\nb Determined from XRF.\nIn response to the description of the catalyst composition, we have added Table S12 for systematic\npresentation to facilitate readers' understanding. And to add further clarification “Loading of\nCo and the other metal additives was 15 wt.% and 0.03~3 wt.%, respectively (Co M N: M and N\nx y\nrepresent metal additives; x and y respectively represent the loading amounts of additives M and N\nCatalysts include: 15Co, 15Co Cs, 15Co Cs, 15Co Cs, 15Co Mn, 15Co Mn, 15Co Mn Cs,\n0.03 0.1 0.3 0.5 1 0.5 0.1\n15Co Mn Cs, 15Co Mn Cs, 15Co Mn Ni, 15Co Mn Ni, 15Co Mn Ni, 15Co Mn Ca,\n1 0.1 1 0.3 0.5 1 0.5 2 0.5 3 0.5 0.1\n15Co Mn Ca, 15Co Mn Cr, 15Co 5Mn Cr, 15Co Mn Cr, 15Co Mn Cr, 15Co Mn Cr,\n0.5 0.3 0.5 2 0. 1 1 1 1 2 2 2\n15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba, 15Co Mn Ba).\n0.5 0.1 0.5 0.3 0.5 0.5 0.5 1 0.5 2 0.5 3\nFinally, the term “net CO₂ emissions” is typically associated with life-cycle analysis. Its use here to\ndescribe a scenario where minor CO₂ side-products are recycled upstream is, in my opinion,\nimprecise and should be revised.\nWe appreciate the insightful suggestions from the Reviewer and have made the corresponding\nrevisions. \"By coupling residual CO with green hydrogen via the reverse water-gas shift reaction\n2\nto recycle syngas, the process might approach net-zero CO emissions, significantly reducing\n2\ngreenhouse gas emissions can be significantly reduced outputs.\"\nReferences\ncatalysts: influence of precursor activation. ACS Catal. 4, 2792-2800, (2014).\nSoc. 135, 7114-7117, (2013).\nselective CO hydrogenation to higher alcohols. ACS Catal. 5, 2929-2934, (2015).\naldehydes/alcohols and olefins/paraffins. Nat. Commun. 7, 13058, (2016).\nmultifunctional catalyst. Angew. Chem. Int. Ed. 58, 4627-4631, (2019).\nalcohols synthesis via syngas conversion. Appl. Catal. B: Environ. 285, 119840 (2021).\nhigher alcohols synthesis from syngas. Appl. Catal. B: Environ. 278, 119262 (2020).\nNature Communications - Manuscript ID: NCOMMS-25-14503B\nResponse to Reviewers\nComments in blue - Replies in black - Actions in bold - Citations in italic\nReviewer #2 (Remarks to the Author):\nAs suggested, the authors have improved the DFT model of the catalyst. Over the last decade, it has\nbeen established that alkylidyne species (CH CH C) are the key reaction intermediates that undergo\n3 2\nhydrogenation, dehydrogenation or CO insertion. Direct olefin hydrogenation is not a relevant\nreaction in Fischer-Tropsch synthesis.\nWe gratefully acknowledge the reviewer for his/her insightful and constructive comments. Instead\nof using olefin hydrogenation as a model reaction, we have now simulated the three key\ntransformation routes for alkylidyne species (CH CH C) on different model catalysts (Figs. 1f,\n3 2\nS8-11 and Table S3), as suggested by the reviewer.\nThe relative energies for the formation of three different products, including oxygenates, olefins,\nand alkanes, were compared. These results clearly show that the hydrogenation of alkylidyne species\nto the corresponding alkane is most favored on Co(111) with the lowest barrier of only 1.05 eV\n(1.09 and 1.34 eV, respectively, on Co C-Co and Cs O-Co C-Co). Instead, the hydrogenation of\n2 2 2\nalkylidyne species to the corresponding olefins on Co(111) is energy-demanding with a barrier of\n1.83 eV, whereas it is only 1.03 and 0.90 eV, respectively, on Co C-Co and Cs O-Co C-\n2 2 2\nCo. For the formation of oxygenates, the CO insertion step is also accompanied with a relatively higher barrier\nof 1.37 eV on metallic Co, in comparison to only 0.86 eV on Co C-Co and 0.82 eV on Cs O-Co C-\n2 2 2\nCo. These newly supplemented DFT results are fully consistent with our experimental data, and\nthus provide a deeper molecular-level understanding of the divergent product distributions on the\ndistinct active sites.\nWe have now replaced Fig. 1f with the newly derived DFT results in the revision, and\nrephrased the discussions accordingly.\n“To explain the different product distributions, three key fundamental steps including\nthe formation of alkanes, olefins, and oxygenates from alkylidyne species (C H CH C*),\n3 7 2\nthe presumed key reaction intermediates, were simulated (Figs. 1f, S8-S11 and Table\nS3). For Co(111), the energy barrier for the formation of alkanes from C H * is much\n5 9\nlower than those for olefins and oxygenates (1.05 vs. 1.83, 1.37 eV), explaining the high\npropensity of deep hydrogenation on pure metallic cobalt. In contrast, the C\n9\n*\nintermediates are more prone to forming C H CHCH * or undergoing CO insertion\n3 7 2\ninstead of hydrogenation to alkanes on Co\nsuggesting that Co C-Co interphase can generally enhance the formations of olefins and oxygenates.\nC H * hydrogenation to alkanes and olefins, CO insertion were calculated and used as\n5 9\na selectivity indicator. A larger difference was observed on Cs O-Co C-Co than on\n2 2\nCo C-Co (0.44 vs. 0.06 eV), explaining the improved selectivity towards\n2\noxygenates/olefins on the former.”\nFig. 1f. Design of efficient syngas-to-oxygenates/olefins catalysts. The reaction coordinate of\nC H CH C* desorption, hydrogenation, and CO insertion pathways on Co(111), Co C-Co, and\n3 7 2 2\nCs O-Co C-Co models. Bader charge analysis were shown in the inset.\n2 2\nFig. S9. Illustrations of different configurations of C H CH C* desorption on the Co(111), Co C-\n3 7 2 2\nCo and Cs O-Co C-Co.\n2 2\nFig. S10. Illustrations of different configurations of C H CH C* hydrogenation on the Co(111),\n3 7 2\nCo C-Co and Cs O-Co C-Co.\n2 2 2\nFig. S11. Illustrations of different configurations of CO* insertion into C H CH C* species on the\n3 7 2\nCo(111), Co C-Co and Cs O-Co C-Co.\n2 2 2\nTable S3. The detailed E, H, S, ZPE, G values for each IS, TS, and FS states of the reaction pathway\nstudied in different calculation models\nModel Adsorbate E ZPE H S G\nCo *CCH C H +*H -474.95 3.534 4.019 0.989 3.030\n2 3 7\nTS -474.27 3.489 3.960 0.956 3.004\n*CHCH C H +* -474.278 3.698 4.219 1.061 3.158\n2 3 7\nTS -472.448 3.370 3.881 1.088 2.793\n*CHCHC H +*H -474.094 3.462 3.967 1.060 2.907\n3 7\nTS -472.934 3.730 4.211 0.988 3.223\n*CH CHC H +* -472.941 3.893 4.377 1.000 3.377\n2 3 7\n*CHCH C H +*H -478.162 3.698 4.219 1.061 3.158\n2 3 7\nTS -477.592 3.730 4.211 0.988 3.223\n*CH CH C H +* -477.964 3.893 4.377 1.000 3.377\n2 2 3 7\n*CH CH C H +*H -481.88 4.083 4.621 1.127 3.495\n2 2 3 7\nTS -480.83 4.037 4.586 1.170 3.416\n*CH CH C H +* -482.229 4.259 4.777 1.144 3.633\n3 2 3 7\n*CHCH C H +*CO -490.867 3.677 4.292 1.265 3.027\n2 3 7\nTS -489.777 3.737 4.344 1.274 3.070\n*COCHCH C H +* -490.13 3.798 4.411 1.287 3.123\n2 3 7\nCo C-Co *CCH C H +*H -969.528 3.513 4.006 1.036 2.970\n2 2 3 7\nTS -968.492 3.470 3.962 1.013 2.949\n*CHCH C H +* -968.527 3.581 4.076 1.028 3.047\n2 3 7\nTS -967.788 3.405 3.917 1.078 2.839\n*CHCHC H +*H -968.934 3.458 3.944 0.964 2.980\n3 7\nTS -967.887 3.389 3.848 0.912 2.936\n*CH CHC H +* -968.642 3.604 4.097 1.028 3.070\n2 3 7\n*CHCH C H +*H -972.649 3.754 4.271 1.046 3.225\n2 3 7\nTS -972.067 3.767 4.256 0.985 3.271\n*CH CH C H +* -972.188 3.891 4.398 1.054 3.345\n2 2 3 7\n*CH CH C H +*H -976.258 4.072 4.613 1.126 3.487\n2 2 3 7\nTS -975.168 4.094 4.577 0.983 3.593\n*CH CH C H +* -976.757 4.255 4.698 0.912 3.786\n3 2 3 7\n*CHCH C H +*CO -985.418 3.768 4.400 1.300 3.100\n2 3 7\nTS -984.556 3.728 4.349 1.271 3.079\n*COCHCH C H +* -984.819 3.779 4.373 1.203 3.170\n2 3 7\nCs O-Co C-Co *CCH C H +*H -983.122 3.528 4.017 0.995 3.023\n2 2 2 3 7\nTS -982.226 3.477 3.967 1.008 2.959\n*CHCH C H +* -982.362 3.588 4.077 1.013 3.065\n2 3 7\nTS -981.784 3.400 3.867 0.945 2.922\n*CHCHC H +*H -982.744 3.477 3.963 0.988 2.975\n3 7\nTS -982.001 3.463 3.927 0.934 2.993\n*CH CHC H +* -982.265 3.591 4.078 0.995 3.084\n2 3 7\n*CHCH C H +*H -986.395 3.767 4.281 1.034 3.247\n2 3 7\nTS -985.455 3.762 4.259 1.022 3.237\n*CH CH C H +* -985.83 3.874 4.380 1.054 3.326\n2 2 3 7\n*CH CH C H +*H -989.829 4.048 4.584 1.105 3.480\n2 2 3 7\nTS -988.487 4.056 4.559 1.075 3.483\n*CH CH C H +* -990.342 4.266 4.786 1.142 3.644\n3 2 3 7\n*CHCH C H +*CO -999.288 3.752 4.377 1.280 3.097\n2 3 7\nTS -998.468 3.711 4.340 1.301 3.039\n*COCHCH C H +* -998.548 3.751 4.353 1.199 3.154\n2 3 7\nIt has also been established that olefins are the primary products of cobalt Fischer-Tropsch synthesis,\nbut thermodynamically, hydrogenation to paraffins is of course favorable and will dominate at\nhigher conversions.\nWe sincerely thank the reviewer for this insightful comment. We fully agree with the reviewer that\nalkane formation is thermodynamically more favored for cobalt-catalyzed Fischer-Tropsch\nsynthesis, particularly at high conversions. We kindly remind the reviewer that, in most of our cases,\nthe single-pass CO conversion was moderate (< 25%).\nMoreover, both kinetic and thermodynamic factors play a decisive role in governing the reaction\npathway and product distribution. As has been discussed in the replies to your previous comments,\nour DFT calculations across the three models reveal that the Cs O-Co C-Co active center\n2 2\nsignificantly lowers the reaction energy barriers for the formation of both olefins and alcohols in\ncomparison to alkanes. These pronounced kinetic effect induced by the proper design of active sites\nshould play a decisive role in steering the products to olefins and oxygenates instead of paraffins.\nReviewer #4 (Remarks to the Author):\nThe authors have further revised their manuscript. Important flaws in the earlier version have been\naddressed, for example the construction of more relevant DFT models and the inclusion of Cs as a\npromoter in a more sensible speciation therein. Other technical aspects have also been improved,\nmaking the manuscript technically more sound.\nWe thank the reviewer for these encouraging remarks. We are glad that the manuscript was found\ntechnically more sound. Further improvements related to the novelty and ASF distribution are\ndiscussed below.\nFor publication in Nature Communications, I still consider that splitting a previously published\nprocess (by the same authors, ACS Catalysis 2021) into two reactors in series, to gain a more\nindependent temperature control, does not constitute a sufficiently solid innovation.\nWe kindly remind the reviewer that this work does not simply spit the previous system into two\nreactors. Instead, we stress that catalyst innovation in FTS and compatibility of different catalytic\nmodules in the current two-bed system are key to the exceptional C alcohol formation.\n4+\nFirst, the discovery of Cs O-modified Co C-Co interfacial sites for olefins- and oxygenates-oriented\n2 2\nsynthesis is novel and pivotal in this study, as it lies a solid foundation for the further transformations\n(hydroformylation, and hydrogenation) of the intermediates. To better explain this point, we have\nperformed an additional test, by accommodating the currently developed three catalysts into\none reactor, and compared the results with those from our previously reported data in ACS\nCatal (see Table R1).\nThe new results demonstrate that the current system not only enhances the catalytic performance\n(CO conversion 35.7% vs. 29.7%), and but also significantly improves C alcohols selectivity\n4+\n(from 23.0% to 47.8%). Our DFT simulations (Fig. 1f) also demonstrate the much lower reaction\nenergy barriers for the olefins/oxygenates formation on Cs O-Co C-Co, in comparison to those on\n2 2\nthe previously established Co C-Co and metallic Co sites. These results ambiguously demonstrated\n2\nthe superior performance of the newly developed Cs O-Co C-Co catalysts in steering the formation\n2 2\nof high alcohols, thus providing valuable insights to guide catalyst design.\nSecond, the compatibility of three catalytic modules is also critical to the optimized C alcohol\n4+\nselectivity. As have been stressed in the previous revision, complex interplays exist in the three\ncascade catalyst beds, primarily owing to the multiple effluents from the front beds. This will\ninevitably cause significant challenges for the design of robust catalysts from downstream\ntransformations, for instance, constructions of monometallic Rh sites to enhance the\nhydroformylation activity toward multi-carbon mixed olefins instead of a single one, and of efficient\nhydrogenation ensembles tolerable of CO poisoning (Fig. 2b) and mitigating the water-gas shift\nside reaction (Fig. 2c). For this reason, we made significant efforts in the screening of different\ncatalyst formulas to finally obtain the optimal combination of the three catalytic modules (Fig. 2a).\nAdditionally, as pointed out by the reviewer, two-bed technology allows for more delicate tuning of\nthe individual catalytic modules to reach the optimal performance. Building upon these results, we\nachieved a record-high C selectivity of 80% at a single pass CO conversion of 17.2%.\n4+\nTable R1. The catalytic performances of different combinations of catalysts in the tandem system\nfor the syngas-to-C alcohols conversion.\n4+\nS / % S C OH\n4+\nCatalysts X / %\nCO\nCH CO C C = aldehydes alcohols\n4 2 2+ 2+\n/ %\nAa 29.7 8.0 5.5 29.1 13.6 16.4 27.4 23\nBa 35.7 5.5 6.8 23.9 3.3 1.1 59.4 48\nCb 17.2 1.3 1.4 10.7 0.0 0.0 86.5 80\nA: Our previous work reported in ACS Catal.\nB and C: This work.\na Reaction conditions: H /CO = 2, F = 65 ml min-1, T = 210 ℃ (syngas-to-oxygenates/olefins and\n2\nhydroformylation/hydrogenation), and P = 3 MPa.\nb Reaction conditions: H /CO = 1.5, F = 130 ml min-1, 210 ℃ (syngas-to-oxygenates/olefins),\n2\n140 ℃ (hydroformylation/hydrogenation) and P = 8 MPa.\nFig. 1f. Design of efficient syngas-to-oxygenates/olefins catalysts. The reaction coordinate of\nC H CH C* desorption, hydrogenation, and CO insertion pathways on Co(111), Co C-Co, and\n3 7 2 2\nCs O-Co C-Co models. Bader charge analysis were shown in the inset.\n2 2\nFig. 2. Compatibility assessment between syngas-to-oxygenates/olefins and the downstream\nhydroformylation or hydrogenation processes. (a) Catalyst performances between syngas-to-\noxygenates/olefins plus hydroformylation (left) and syngas-to-oxygenates/olefins plus\nhydrogenation (right). Reaction conditions: 210 °C (syngas-to-oxygenates/olefins) and 140 °C\n(hydroformylation/hydrogenation), H /CO = 1.5, 3.0 MPa, F = 65 ml min-1. (b) Catalytic\n2\nperformances of 5Pt/TiO and 5Pt4Sn/TiO for valeraldehyde hydrogenation in H and syngas\n2 2 2\nstreams. Reaction conditions: 5Pt/TiO or 5Pt4Sn/TiO , 1.5 g; T = 140 ℃; P = 3.0 MPa; F\n2 2\n(valeraldehyde) = 0.01 ml min-1; F (H ) or F (H /CO = 2) = 30 ml min-1. (c) WGS performances\n2 2\nand CO uptakes of CuZnAl, Cu/SiO , and CuZrO /SiO . Reaction conditions: catalysts 1.5 g; T =\n2 2 2\n140 ℃; P = 3.0 MPa; F (H O) = 0.01 ml min-1; F (CO) = 30 ml min-1. (d) Valeraldehyde\n2\nhydrogenation reaction pathways on Cu(111) and CuZrO model system.\nthe authors claim to achieve a selectivity to C alcohols above 80%, following an ASF distribution\n4+\nwith a chain growth probability of approximately 0.67 (Figure S3). This is presented as a major\nachievement of this study. However, for said chain growth probability, the mathematically derived\nabsolute maximum carbon selectivity to all products with four or more carbon atoms (C ) is\n4+\napproximately 60%. How, then, can the authors report selectivities to C alcohols as high as 80%?\n4+\nIn my view, this strongly suggests issues in the product analysis and/or data treatment. It is similarly\nsurprising that alcohols as short as C and C (methanol, ethanol) follow the same ASF distribution,\n1 2\ndespite the fact that neither of those could be produced by hydroformylation of olefins. All in all, I\nbelieve this study still requires substantial technical revision, including a critical assessment of\nproduct analysis and carbon balances, before it can be considered for publication.\nWe sincerely thank the reviewer for the careful evaluation. We are sorry for not clearly clarifying\nthe relations between the α values from ASF distribution and the C alcohol selectivity in the\n4+\nprevious revision. We kindly reminded the reviewer that the α values reported in previous Fig. S3\nwas associated only with FTS reaction, not for the integrated systems. As more complicated\nreactions can occur in the integrated systems, including hydroformylation, hydrogenation and etc.,\nthe product selectivity in the integrated system can be significantly deviated from the single-step\nFTS reaction.\nTo address this and to explain for the high C alcohol selectivity of the developed integrated\n4+\nsystems, we have now also plotted the product distribution of the integrated systems and\ncompared the α values between single-step FTS and the integrated ones (Fig. S3e,f, Table R2). \nSeveral features are noteworthy,\ni) For the FTS, all the catalysts follow the standard linear ASF distribution, the theoretical C\n4+\nselectivity is roughly ~56-60% (α=0.65-0.67) at 3 MPa, and ca. ~69% (α=0.72) at elevated pressure\nof 8 MPa (indicating the favorable chain-growth probability at higher pressures);\nii) In our real integrated systems, mainly due to the chain elongation via hydroformylation (C\nn\nolefins → C aldehydes, olefins selectivity of the FTS products: approximately 30%, Table S1),\nn+1\nC products still follow the linear relation but C -C products show strong deviation. We then\n4+ 1 3\ncalculated the α values of the integrated systems starting from C . By assuming that C -C will\n4 1 3\nfollow the same trend, the theoretical C selectivity of the integrated systems can be estimated, i.e.,\n4+\n~63% (α=0.68) and ~69% (α=0.72), respectively, at 3 and 8 MPa. These theoretical values are still\nlower than our reported C alcohol selectivity of 68% (3 MPa) and 80% (8 MPa), which can be\n4+\nreasonably explained by the strong deviation of C -C products from the ASF distribution\n1 3\nleading to largely underestimated values.\nBased on the above reasoning, we trust our results on C alcohol selectivity are reasonable.\n4+\nWe have now provided the ASF plots of both individual FTS and integrated systems in revised\nFig. S3, and the results are briefly discussed in the revised piece.\nFig. S3 Products chain lengthening. Detailed selectivity patterns and Anderson-Schulz-Flory\n(ASF) chain-lengthening characteristics of the various product classes over (a) Co Cs/C (3 MPa), (b)\n0.1\nCo Mn/C (3 MPa), (c) Co Mn Cs/C (3 MPa), (d) Co Mn Cs/C (8 MPa). (e) integrated system\n0.5 0.5 0.1 0.5 0.1\n(3 MPa), (f) integrated system (8 MPa)\n“Anderson-Schulz-Flory (ASF) plots have been constructed and are compiled in Fig. S3a-d.\nAccordingly, a linear ASF behavior with chain lengthening probability  = 0.65 is obtained, and as\nthe pressure increased to 8 MPa, α increased to 0.72. Control experiments showed that additions of\nindividual Mn or Cs could also improve the total selectivity of oxygenates/olefins and reduce CH\n4\nselectivity, with α values of 0.67 and 0.66, respectively, but both led to decreased activity (Table\nS1).”\n“In the integrated system, the C -C products strongly deviate from the ASF linear distribution, and\n1 3\nthe chain growth probability α increases from 0.65 to 0.68, indicating that the hydroformylation\nprocess effectively modulates product distribution (Fig. S3). As the reaction pressure increased from\n3.0 to 8.0 MPa, the deviation of C -C products from the ASF linear distribution became\n1 3\nincreasingly pronounced (Fig. S3e,f), while the chain growth probability α rose from 0.68±0.01 to\n0.72±0.01, demonstrating that elevated pressure enhances carbon chain elongation and suppresses\nthe formation of low-carbon products.”\nFurthermore, to resolve concerns regarding product quantification and carbon balance, we have\nrecalculated the total carbon input using precise measurements of feed gas (syngas) flow rate\nand composition (Tables R2, R3). The total carbon output was determined by summing the carbon\ncontent across all product streams, including liquid phases (organic and aqueous), solid wax, and\ngaseous components in the tail gas. This comprehensive and quantitative approach ensured a carbon\nbalance within 100±5%, robustly validating the accuracy and reliability of our product analysis.\nTable R2. Carbon balance summary table a (3 MPa)\nCarbon molar flow rate in the\n1671.4\nfeed gas / mmol\nInput\nTotal carbon input / mmol 1671.4\nCarbon molar flow rate in the\n1457.3\noff-gas / mmol\nCarbon molar flow rate in the\n20.0\naqueous phase / mmol\nCarbon molar flow rate in the\nOutput 114.9\noil phase / mmol\nCarbon molar flow rate in the\n56.5\nwax phase / mmol\nTotal carbon output / mmol 1648.7\nCarbon balance 98.6%\nTable R3. Carbon balance summary table a (8 MPa)\nCarbon molar flow rate in the\n1671.4\nfeed gas / mmol\nInput\nTotal carbon input / mmol 1671.4\nCarbon molar flow rate in the\n1400.7\nOutput off-gas / mmol\nCarbon molar flow rate in the 6.4\naqueous phase / mmol\nCarbon molar flow rate in the\n127.6\noil phase / mmol\nCarbon molar flow rate in the\n115.3\nwax phase / mmol\nTotal carbon output / mmol 1650.0\nCarbon balance 98.7%\naAfter stabilization for 24 hours, carbon balance data were obtained by sampling at 12 h intervals.\nReaction conditions: H /CO = 1.5, F = 130 ml min-1, 210 ℃ (syngas-to-oxygenates/olefins), 140 ℃\n2\n(hydroformylation/hydrogenation).\nWe have now described the carbon balance in the revision.\n“A comprehensive analysis, including liquid phases (organic and aqueous), solid wax, and gaseous\ncomponents, leads to excellent carbon balances (generally within 100±5%).”"}, {"round": 3, "reviewer_comments": {"reviewer_2": "The authors have replaced the original DFT simulations with more relevant simulations to support the experimental results. I have no additional comments.", "reviewer_4": "The current revised version of the manuscript can be recommended for publication."}, "author_response": ""}]

Decision letter