Built-in tandem catalysis in hierarchical pores for efficient vinyl chloride production

Domain: chemistry
Published: 2026-03-07
Editorial outcome: major_revision

Abstract
Tandem catalysis over disparate active sites is frequently designed to promote the catalytic
efficiency for industrial reactions. Herein, a built-in tandem system in a single hierarchical porous
catalyst is constructed for vinyl chloride production from ethylene dichloride and acetylene
cascade. Using a pore-selective filling strategy, Ru, CuRu, and AuRu components are sequentially
confined in the macro-, meso- and micropores of carbon material. Mechanism study shows that
ethylene-dichloride dehydrochlorination occurs on macropore Ru sites, generating vinyl chloride.
H and Cl radicals react with acetylene on mesopore CuRu sites, and the residual acetylene is
hydrochlorinated over micropore AuRu sites. The stronger acetylene adsorption of CuRu and
AuRu in a VCM-rich atmosphere enables acetylene conversion near the thermodynamic limit and
stable operation for 1200 h on stream. This built-in tandem catalysis in hierarchical pores provides
a general paradigm for cascade reactions in a single porous catalyst.

Introduction
Poly-vinyl chloride (PVC) has become the third-largest synthetic polymer with a worldwide
production over 30 million tons per year.1 The vinyl chloride monomer (VCM) can be industrially
produced by the ethylene oxychlorination reaction, 2 which however relies heavily on oil-derived
feedstocks. For coal-rich countries, acetylene hydrochlorination is the preferred route for VCM
synthesis,3-8 but its large-scale application is still hampered by the use of toxic mercury chloride
(HgCl /C) catalysts.9-11 Recently, ethylene-dichloride and acetylene cascade (EAC) to produce
2
VCM12-15 (CH ClCH Cl + C H = 2CH CHCl, ΔH0 = – 29 kJ mol-1) has attracted increasing
2 2 2 2 2
attention. EAC combining the oil- and coal-derived feedstocks, which can alleviate energy
constraints and avoid the use of HgCl /C catalysts. Meanwhile, the EAC process produces
2
stoichiometric VCM, thus saving the tedious product purification. Classical EAC is composed of
two distinct steps involving the endothermic decomposition of ethylene-dichloride (step 1:
CH ClCH Cl = CH CHCl + HCl, ΔH0 = 69 kJ mol-1) and the following exothermic acetylene
2 2 2
hydrochlorination (step 2: C H + HCl = CH CHCl, ΔH0 = – 98 kJ mol-1). The opposite thermal
2 2 2
demands make it challenging to coordinate the two steps (step 1-2) on a single active site.
Moreover, the product VCM shares a similar π-conjugated structure with acetylene,15, 16 leading
to competitive adsorption on the same active site. This makes it difficult to achieve a complete
conversion of acetylene even at an ultra-low space velocity. Recent density functional theory
(DFT) works have also demonstrated that the adsorption of VCM and related small molecules is
highly sensitive to surface composition and electronic structure.17-19 Therefore, it will be rational
to construct a tandem catalytic system by guiding the sequential ethylene-dichloride
decomposition and acetylene hydrochlorination reactions over different active sites.

Process engineering using two-stage cascaded reactors with distinct catalysts has been practiced
in VCM manufacture.20, 21 The catalyst loaded in the second reactor is responsible for the
continuous conversion of the unreacted acetylene from the first reactor. Researchers have also
explored an alternative stacked catalyst-bed tandem system with a C N /AC catalyst layered on
3 4
top of an Au/C N /AC catalyst,20 which could effectively separate the ethylene-dichloride
3 4
dehydrochlorination and acetylene hydrochlorination processes. Despite the above endeavors, the
multiscale tandem configuration still cannot deliver satisfactory VCM productivity, which is
hindered by the inefficient spatiotemporal transfer of the reaction intermediates (e.g., short-lived
Cl and H radicals derived from step 1). Meanwhile, precisely matching the desired catalyst
functions with the varying reactant composition remains challenging.

Herein, the hierarchical porous carbon was used as a catalytic reactor, wherein the reactants
promptly flow within the interconnected channels, cascading from macropores to mesopores and
further to micropores. A novel built-in tandem catalysis within hierarchical pores was orchestrated,
in which specific active components located in macropores, mesopores, and micropores,
synergistically catalyze the EAC reaction. By screening a variety of components, Ru was selected
to occupy the macropores, being responsible for catalyzing the ethylene-dichloride decomposition.
CuRu and AuRu, which possess higher acetylene adsorption capability in a VCM-enriched
atmosphere, were confined in the mesopores and micropores, respectively, where they drive the
acetylene hydrochlorination reaction. A strategic selective pore filling strategy was successfully
implemented to enable the precise injection of Ru, CuRu and AuRu into macropores, mesopores
and micropores, selectively (Ru -CuRu -AuRu /NPC catalyst). Consequently, the
macro meso micro
catalyst demonstrated excellent catalytic activity for EAC with the acetylene conversion achieving
the thermodynamic limit. The catalyst showed robust stability during the 1200 h reaction time.
With systematic characterizations and DFT calculations, the built-in tandem catalysis mechanism
in hierarchical pores was elucidated. We believe the advanced tandem catalysis system developed
in this work could offer a universal platform for catalyzing EAC and other significant cascade
reactions.

Results
Catalyst selection for ethylene-dichloride and acetylene cascade

Ethylene-dichloride and acetylene cascade (EAC) was performed in a fixed-bed micro-reactor
(Supplementary Figure 1), which integrates endothermic ethylene-dichloride dehydrochlorination
and the following exothermic acetylene hydrochlorination (Supplementary Discussion 2.1:
Supplementary Figures 2, 3; Supplementary Table 1), with acetylene activation having been
proved to be the rate-determining step14 (Supplementary Discussion 2.2: Supplementary Figures
4-9). As previously reported,1, 2, 13, 15 N, P doping in carbon has been shown to be activated in
promoting dehydrochlorination (Supplementary Table 2) and acetylene hydrochlorination21
(Supplementary Table 3). Therefore, herein, N, P-doped porous carbon (NPC) was engineered by
carbonization of ionic-liquids, which enabled simultaneous heteroatom doping and hierarchical
pore formation through nanoscale ion-cluster templating.22 By independently measuring the EAC
performance over the upper (bed-I), middle (bed-II), and bottom (bed-III) catalyst beds of NPC
(Figure 1-a1), it is interesting to observe that ~80% acetylene is converted in the upper bed-I.
However, further acetylene conversion is inhibited in the lower region (bed-II, -III, Figure 1b).
Given the exothermic nature of EAC (Supplementary Table 4), temperature variations may serve
as powerful indicators of reactant conversion. By in-situ tracking the temperature at different
position of the catalyst bed during the reaction, it was observed that there is a significant
temperature rise (>20 K) in bed-I (Supplementary Figure 10), while negligible temperature
variation is detected in bed-II, -III. The mass transfer limitations are completely excluded in EAC
(Supplementary Discussion 2.3). This therefore proved the poor reactivity of the downstream
catalysts, which is likely caused by the VCM accumulation,23,24 hindering the adsorption of the
reactants (acetylene and/or EDC). In this regard, transient response transformation experiments
were performed to validate the influence of VCM on reactants adsorption. It is confirmed that EDC
adsorption is hardly affected by VCM, but acetylene adsorption is significantly hindered in a
VCM-enriched atmosphere (Supplementary Figures 11-13). This is attributed to the competitive
adsorption of VCM and acetylene,1, 4, 10, 16 due to their similar σ and π bonding. To this end, two
cascade reactors are commonly applied in industry21 (Figure 1-a2) with the second reactor
responsible for the continuous conversion of the residual acetylene from the first reactor.
Alternatively, another promising tactic is to build a tandem catalysis system, placing catalysts with
stronger acetylene adsorption capabilities in the lower catalyst bed to guarantee a complete
acetylene conversion under a high-VCM-concentration atmosphere.

To the best of our knowledge, Au,25-29 Ru30-33 and Cu34-37 are the most explored components for
activating acetylene, which are anticipated to be qualified to catalyze the EAC process. Thus, the
acetylene conversion capability was first screened using various components, including Au, Ru,
Cu, AuRu, CuRu and AuCu, in VCM-enriched atmosphere (~20 vol.% C H , 20 vol.% EDC, and
2 2
60 vol.% VCM in Figure 1-a2). AuRu/NPC exhibits the highest activity (Figure 1c), however, it
deactivates the fastest under accelerated deactivation reaction conditions (10,000 h-1,
Supplementary Figure 14), likely due to coke deposition on bimetallic Au-based catalysts23.
In comparison, Ru/NPC and CuRu/NPC show slightly inferior catalytic activity, while their
durability is higher than that of AuRu/NPC. Consequently, AuRu/NPC, Ru/NPC and CuRu/NPC
are selected as the optimal catalyst components (detailed in Supplementary Figure 14). To balance
activity and durability, and optimize the cascaded process, a ternary-catalyst-bed (Figure 1-a3)
was constructed. A better trade-off between activity and durability is achieved from the optimized
stacking mode of Ru/NPC(upper)-CuRu/NPC(middle)-AuRu/NPC(bottom) than from other
combinations (Supplementary Figure 14). The high performance likely arises from the
progressively increased acetylene adsorption capacity from the upper to the bottom catalyst bed.
This is confirmed by the highest C H desorption temperature and desorption amount for
2 2
AuRu/NPC in the C H -TPD graph in Figure 1d, thereby ensuring the tandem conversion of
2 2
acetylene in VCM-enriched atmosphere.

The above results sufficiently underline the efficacy of the tandem catalysis by constructing a
ternary-catalyst-bed. In practical heterogeneous catalytic process, the feed flows from macropores
→ mesopores → micropores in the hierarchical pores of the catalysts,38 which mimics the flow
routes from top to bottom in the catalyst bed with differentiated reactant concentrations. This
inspires us to establish the tandem catalysis system by confining selected metallic components of
Ru, CuRu and AuRu in macropores, mesopores and micropores, separately, to judiciously match
the catalyst adsorption capability with the gradient reactant concentrations, which has not been
explored before (Figure 1-a4).

Construction of built-in tandem catalysis in hierarchical pores

To confine specific metallic components in targeted pores, a pore-selective filling strategy was
developed. Capillary forces are well known to drive solvent infiltration into porous materials
during impregnation,39,40 following the sequence: micropores → mesopores → macropores.
Therefore, we can first selectively impregnate metallic components into micropores using an
amount of metal solution equivalent to the micropore volume, followed by calcination to
decompose the precursor, resulting in the target micropore-confined metal catalyst (M1 ). To
micro
load catalysts into mesopores, micropores are protected by pre-filling with a blocking agent
(containing no metals). Then, another immiscible solvent carrying the second metal species is used
to fill the mesopores via an equivalent-mesopore-volume impregnation method, followed by
calcination to obtain M2 -M1 . By analogy, a similar procedure was repeated to build the
meso micro
final ternary M3 -M2 -M1 tandem porous catalyst. Specifically, the previously screened
macro meso micro
Ru, CuRu and AuRu were selected as catalysts to occupy the positions in the macropores,
mesopores and micropores, respectively, for the preparation of Ru -CuRu -AuRu /NPC
macro meso micro
with NPC serving as support. Detailed pore filling characterizations and discussions were shown
in Figures 2a-2c, Supplementary Figures 15-18 and Supplementary Tables 5, 6. These results
indicate that the micropores are nearly saturated at ~20 vol.% solvent filling, the mesopores are
effectively blocked at ~50 vol.%, and further filling progressively seals the macropores.

In brief, the ionic liquid [BMIM+-Tf N-] (IL3, Supplementary Figure 19) was applied as the
2
sacrificial blocking agents for pore blocking and another immiscible ionic liquid [BMIM+-Cl-]
(IL4) was used as the solvent for dissolving metal precursors. As illustrated in the schematic
diagram (Figure 2a), the following steps involved: (I) Micropore Filling. RuCl and HAuCl were
3 4
dissolved in IL4 (volume equivalent to micropores) and dropwise loaded into the NPC support.
The microporous filling was confirmed by the disappearance of micropores in the pore volume
distribution (steps 1-2, Figure 2c). Subsequent calcination at 587 K decomposed IL4 and metal
precursors, anchoring the metal components in the micropores and releasing the microporous space
(step 3, Figure 2c); (II) Mesopore Filling. The micropores were pre-protected using IL3, which is
immiscible with IL4. Then, RuCl and CuCl dissolved in IL4 were introduced into the mesopores,
3 2
followed by calcination at 587 K to decompose IL4 and the metal precursors. IL3 remained intact
in the micropores due to its higher decomposition temperature (Figure 2b); (III) Macropore Filling.
IL3 blocked the mesopores, and RuCl dissolved in IL4 was loaded into the macropores. The final
3
calcination at 776 K decomposed IL4, IL3, and the metal precursors, yielding the Ru -
macro
CuRu -AuRu /NPC catalyst. The stepwise pore filling and release processes were validated
meso micro
by variations in pore volume distribution (Figure 2c, Supplementary Table 6). As references,
individual pore-confined catalysts (e.g., Ru /NPC) and dual-pore-confined catalysts (e.g.,
macro
Ru -CuRu /NPC) were fabricated with similar procedures.
macro meso

To further visualize the spatial distribution of metal species within the hierarchical pores,
focused ion beam-scanning electron microscopy (FIB-SEM) was performed on Ru -CuRu -
macro meso
AuRu /NPC (Figure 2d). A cross section with a length of 19.75 μm and a milling depth of 6.11
micro
μm was opened on a representative catalyst surface (Figure 2-d1), where macropores, mesopores
and micropores are clearly observed, respectively. Elemental line-scan profiles across these
regions (Figure 2-d2) show that Ru gives a dominant signal in the macropore region, while Cu and
Au are nearly undetectable, indicating that Ru species mainly occupy macropores. In the mesopore
region, both Cu and Ru are detected with comparable intensity, proving that CuRu sites are
confined in mesopores. In contrast, the micropore-rich region exhibits strong Au and Ru signals
with negligible Cu, evidencing the preferential location of AuRu sites in micropores. The FIB-
SEM results may offer direct evidence for the catalyst location, sufficiently proving the efficacy
of the capillarity-driven and the pore-selective filling strategy.

The atomic configurations of the metal species are explored by X-ray absorption spectroscopy
(XAS). The X-ray absorption near edge structure (XANES, Supplementary Figure 20) shows that
the adsorption edge energies of Au, Ru, and Cu in the Ru -CuRu -AuRu /NPC catalyst
macro meso micro
are higher than those of the corresponding metallic foils, indicating their high valence features.
The corresponding Fourier transforms (FT) are displayed in Figure 2e and Supplementary Figures
21-23. Au species exhibited a single metal-neighboring shell peak (Figure 2-e1) corresponding to
Au-N,41 with a bond distance of 1.99 Å (Supplementary Table 7). The absence of Au-Au intensity
around 2.2 Å at the corresponding wavelet transform (WT, Figure 2-f1) confirms the atomic states
of Au. For Ru species, the scattering paths of Ru-N (2.00 Å)42 and Ru-Cu/Ru (2.56 Å)43, 44 are
detected (Figure 2-e2). However, overlapping peak positions make it difficult to distinguish Ru-
Ru and Ru-Cu coordination in the Ru-based WT spectra (Figure 2-f2). The Ru-Cu coordination
was further accurately identified from mesoporous Cu-based R-space, where Cu-Ru and Cu-N
bonds were observed (Figure 2-e3). Two intensity maxima at approximately 1.9 Å and 2.6 Å in
the WT spectra confirmed the presence of Cu-N21 and Cu-Ru43 bonds (Figure 2-f3). Noting that
the coordination number of Ru-Cu/Ru in the Ru-based fitting result is 5.9 ± 0.2 (Supplementary
Table 7), and 1.2 ± 0.3 for the Cu-Ru coordination in Cu-based fitting, this implied the existence
of surplus Ru-Ru coordination in macropores and micropores. Due to the disordered organization
in hierarchical pores, it is challenging to directly distinguish the metallic dispersion for Ru -
macro
CuRu -AuRu /NPC by HAADF-STEM characterization (Supplementary Figure 24). To
meso micro
address this, the reference single pore-confined catalysts (Ru /NPC, CuRu /NPC and
macro meso
AuRu /NPC) were studied. HAADF-STEM and atomic structure simulations revealed that Ru
micro
exists as atomic clusters in macropores (Ru ACs, Figures 2-g, h1). Cu/Ru presents as diatomic
single-atoms in mesopores (Cu/Ru SAs, Figures 2-g, h2). And Au single-atoms and Ru atomic
clusters are confined in micropores (Au SAs-Ru ACs, Figures 2-g, h3). These metallic sites are
thermodynamically stable (Supplementary Figure 25) and align well with the XAS analysis. The
pore-specific configurations can be rationalized by considering the metal–metal cohesive
energies.45 Ru exhibits a strong intrinsic tendency to aggregate (E : –7.11 eV, Supplementary
c
Table 8), which dominates over coordination stabilization even in micropores, leading to
nanocluster formation in both macro- and micropores. In contrast, Au shows weak self-cohesion
(–3.52 eV) but strong affinity toward Au-N coordination,41 thus preferentially stabilizing as
isolated atoms. In mesopores, the high Cu/Ru heteronuclear cohesive energy (–7.49 eV), along
with adequate spatial allowance, favors the formation of thermodynamically stable diatomic sites
over separate nucleation. These trends align with the observed configurations (Figures 2g, h) and
confirm that the final structures arise from thermodynamic control rather than random distribution.
Once these pore-specific sites are thermodynamically established, they remain spatially
immobilized during calcination. The metal precursors decompose and anchor in solid form, and
the available thermal energy (0.05–0.07 eV at 587–776 K) is far below the migration barriers (0.2–
0.9 eV, Supplementary Figure 25) required for inter-pore relocation. Overall, the above
configurations in distinct pores are determined by cross-validating four orthogonal techniques of
FIB-SEM, XAS coordination environments, reference single-pore configurations, and energetics,
which collectively exclude alternative scenarios and support a structurally differentiated pore-
specific arrangement.

Catalytic performance evaluation

Bader charge calculations and DOS analysis revealed that the designed metallic components
exhibit a strong capacity to capture acetylene in VCM-rich atmosphere (detailed in Supplementary
Figures 26-36, Supplementary Tables 9, 10), providing a theoretical basis for acetylene conversion
under high VCM concentrations. As shown in Figure 3a, the Ru -CuRu -AuRu /NPC
macro meso micro
catalyst displays the highest reaction rate, approximately 1.2 times that of Ru -CuRu /NPC,
macro meso
and ~1.4 times that of Ru /NPC, highlighting the efficacy of the built-in tandem porous
macro
catalysis. Figure 3b shows the adsorption energy difference, ΔE = E (C H )-E (VCM),
ads ads 2 2 ads
over
Ru, CuRu and AuRu sites are –0.73 eV, –0.91 eV, and –1.52 eV, respectively, indicating that the
acetylene adsorption capacity in VCM-enriched atmosphere follows AuRu > CuRu > Ru, which
is consistent with the experimental results (Figure 1d). This strongly supports the strategy of
optimally orchestrating AuRu in micropores, CuRu in mesopores, and Ru in macropores to achieve
tandem catalysis, consistent with the confirmed stacking order in the ternary-bed evaluation system
(Figure 1-a4).

To evaluate the intrinsic activity, the influence of the catalyst-bed length on reactivity was
investigated. Merely elongating the bed of the Ru /NPC catalyst did not increase the acetylene
macro
conversion beyond 92% (Figure 3c), indicating its limited ability to sustain acetylene capture in a
VCM-enriched environment. By introducing mesopore-confined CuRu (Ru -CuRu /NPC),
macro meso
a promoted acetylene conversion of ~98.2% is achieved. The ternary catalyst (Ru
macro
-CuRu
meso
-
AuRu
micro
/NPC) achieved the highest acetylene conversion of 99.3%, approaching the
thermodynamic limit of 99.8% (Supplementary Discussion 2.1). Notably, the catalyst bed length
required to reach the highest acetylene conversion is significantly shortened for Ru -CuRu -
macro meso
AuRu /NPC (indicated as red shading, Figure 3c), confirming the effectiveness of the built-in
micro
tandem catalysis in hierarchical pores for enhancing the reactant adsorption and activation.
Interestingly, despite extending the catalyst bed length, the conversion over Ru /NPC and
macro
Ru -CuRu /NPC systems remained significantly below the thermodynamic limit. This
macro meso
suggests that, beyond intrinsic activity differences, these catalysts may suffer from internal porous
diffusion effects, which restrict the effective utilization of downstream active sites in VCM-rich
environments. In such cases, stronger C H adsorption alone (Figure 3b) is insufficient to sustain
2 2
conversion unless mass transport toward active centers is efficiently maintained. The hierarchical
Ru -CuRu -AuRu /NPC architecture addresses this limitation by spatially segmenting
macro meso micro
active sites. This gradient-resolved configuration minimizes internal diffusion resistance and
ensures reactant progression aligns with site-specific chemical demands, thereby achieving near-
equilibrium conversion.

Besides the catalytic activity, stability is another key criterion for practical application. The
Ru -CuRu -AuRu /NPC catalyst exhibits superior durability over 500 h on stream at a
macro meso micro
higher space velocity of 320 h-1 (Figure 3d, Supplementary Table 11). In contrast, the most active
AuRu component of the AuRu -AuRu -AuRu /NPC shows lower durability, likely due
macro meso micro
to the reported carbon deposition,23 as evidenced by its sharply decreased specific surface area
(Supplementary Figure 37). For the AuRu -AuRu -AuRu /NPC catalyst, more energy is
macro meso micro
required to release the generated VCM compared with the other two catalytic systems (embedded
in Figure 3d, Supplementary Figures 38, 39). This indicates that VCM tends to cover the AuRu-
based catalyst surface, resulting in the pore blockage. Moreover, the Ru
macro
-CuRu
meso
-
AuRu
micro
/NPC catalyst shows higher activity than the ternary-bed system composed of
[Ru /NPC + CuRu /NPC + AuRu /NPC], highlighting the facilitated tandem contribution
macro meso micro
within hierarchical pores (Figure 3d). This is consistent with the above discussion on the length of
the catalyst bed (Figure 3c). The enhanced stability and activity of the built-in Ru -CuRu -
macro meso
AuRu /NPC catalyst are not solely due to compositional synergy, but also arise from a structural
micro
advantage in coordinating mass transport and sequential reactivity. Unlike conventional tandem
beds with macroscopic interfaces, the hierarchical architecture embeds spatially ordered metal
sites within a single porous matrix, minimizing diffusion distances and facilitating timely
intermediate turnover. This configuration mitigates VCM accumulation and active site blockage,
thus reducing carbon deposition and deactivation risks. These findings provide a structural-
functional integration beyond simple material optimization.

Tandem catalysis mechanism

The gaseous flow sequence in porous materials typically follows the order of macropores,
mesopores, and micropores. This sequence is fundamentally governed by pore size-dependent flow
mechanisms, with larger pores offering lower resistance and dominant viscous flow, while smaller
pores exhibit Knudsen diffusion.46, 47 For tandem catalysis within hierarchical pores, macropore-
confined Ru sites are served as the starting sites for the dehydrochlorination of EDC (EDC →
VCM + HCl) due to its highest EDC adsorption capacity than other porous sites (Supplementary
Figure 40), which is evidenced by the generated HCl signal (Supplementary Figure 41).
Meanwhile, the formation of Cl* radicals was directly verified by electron spin resonance (ESR)
measurements (Figure 4b inset), which shows characteristic radical signals as a function of time
(Supplementary Figure 42), consistent with reported Cl* features.48,49 These results indicate partial
HCl dissociation (HCl → Cl* + H*). Based on experimental results, the desorption of VCM and
HCl (black lines, steps a-c in Figures 4a, 4b) and the generation of H* and Cl* were modeled (steps
c-d for energies in Figures 4a and diagrams in 4b), following the thermodynamic trend with a
lowest activation energy of 0.27 eV (inset black histogram in Figure 4a). The above reaction
process is referred as the ‘EDC decomposition’ process in subsequent discussion.

To study the probability of other pathways occurring at the Ru site, three additional
thermodynamically unfavorable pathways were calculated: the one-step reaction of acetylene and
EDC (C H + EDC → 2VCM, yellow lines in Figure 4a), acetylene hydrochlorination (C H +
2 2 2 2
HCl → VCM, blue lines in Figure 4a), and the radical reaction pathway (C H + Cl* + H* → VCM,
2 2
red lines in Figure 4a). Detailed reaction energies are listed in the under region of Figure 4a
(thermodynamically favorable), while their diagrams are shown in Supplementary Figures 43-45.
Among these routes, the minimum activation energy is the acetylene hydrochlorination pathway
(0.51 eV, inset blue histogram in Figure 4a), which is significantly higher than that of the proposed
EDC decomposition process (inset black route, 0.27 eV). Therefore, both theoretical calculations
and experimental results confirm that the EDC decomposition is the only feasible pathway over
the Ru site. The reaction intermediates generated at the Ru site can migrate to other porous sites,
potentially triggering synergistic effects. Compared with EDC, acetylene exhibits stronger
adsorption on mesoporous CuRu and microporous AuRu (Supplementary Figure 40). Obviously,
EDC decomposition is hindered if the sites are preferential adsorbed by acetylene. In addition, the
conversion of EDC over the macroporous Ru site is 99.54%, and that of acetylene is 92%
(Supplementary Figure 46), which means that EDC was essentially completely converted at the
Ru site, while the subsequent mesoporous and microporous sites are responsible for the residual
acetylene conversion.

The extreme lack of EDC makes it impossible to trigger the one-step reaction of acetylene and
EDC on CuRu and AuRu sites, supported by their extremely high activation energies (1.64, 2.51
eV, yellow lines/histograms in Figure 4a). For the mesoporous CuRu site, the radical pathways
exhibit the lowest energy barrier of 0.41 eV (red lines in Figure 4a), which is lower than that of
acetylene hydrochlorination pathway (0.45 eV) and one-step reaction of acetylene and EDC (1.64
eV). In contrast, acetylene hydrochlorination is favored over the AuRu site, (blue lines in Figure
4a), with an activation energy of 0.49 eV, lower than that of 1.20 eV for the radical pathways and
2.51 eV for the one-step reaction. These findings demonstrate that the lowest energy pathways
catalyzed on mesoporous CuRu and microporous AuRu sites are radical reactions and acetylene
hydrochlorination, respectively.

Importantly, the sequential activation along the macropore → mesopore → micropore is not
arbitrary but thermodynamically enforced. Once EDC is fully reacted at macroporous Ru sites
(99.54% conversion, Supplementary Figure 46), its downstream concentration is nearly zero,
making EDC-involving pathways on CuRu and AuRu sites both thermodynamically disallowed
and kinetically prohibitive. DFT calculations reveal prohibitively high barriers for EAC on CuRu
(1.64 eV) and AuRu (2.51 eV) sites, and no appreciable EDC adsorption (Supplementary Figure
40), thereby excluding reversed or randomized reaction sequences, such as
micropore → mesopore → macropore. Further kinetic analysis reveals that multiple reaction
pathways coexist owing to the different reaction orders of the reactants (Supplementary Figure
47). The superior performance of the three-pore Ru -CuRu -AuRu /NPC system over the
macro meso micro
two-pore configurations Ru -CuRu /NPC and Ru -AuRu /NPC (Supplementary
macro meso macro micro
Figures 48, 49) powerfully validates the feasibility of a tandem catalytic route through hierarchical
pores. The guiding descriptor, ΔE = E (C H )-E (VCM), effectively identifies the active site
ads ads 2 2 ads
confinement within pores, ensuring the tandem conversion of acetylene in mesopores and
micropores. These findings validate the directionality and pore-function assignment of the built-
in tandem system. Therefore, optimal reaction pathways have been identified (Figure 4b).
Specifically, ethylene-dichloride first undergoes hydrogen chloride removal at the Ru site (steps
a-c), followed by the generation of VCM and HCl (steps c-d). Part of the HCl is dissociated to H
and Cl radicals (step d). These species migrate and engage in addition reactions with acetylene at
the CuRu (steps e, f) and AuRu sites (steps i, j), ensuring minimal energy barriers for VCM
production (steps g, h, k). At CuRu sites, acetylene reacts with radicals, while classical acetylene
hydrochlorination occurs at AuRu sites.

In conventional tandem systems,50 where catalytic sites are spatially separated across distinct
catalyst beds and/or reactors, the transfer of reaction intermediates (e.g. short-lived intermediates
such as H* and Cl*) is often hindered by long diffusion distances and interfacial mismatches. These
constraints increase the likelihood of radical recombination or side reactions, leading to poor
catalytic continuity, downstream deactivation, and local carbon accumulation. In contrast, the
hierarchical porous architecture developed here integrates functionally matched active sites within
a single catalyst, enabling rapid, nanometer-scale progression of reactive species. This structural
proximity ensures efficient intermediate turnover while minimizing their undesired accumulation,
thus effectively reducing surface blockage and coke formation. The resulting integration of pore-
scale transport and site-specific reactivity accounts for the superior activity and long-term stability
of the Ru -CuRu -AuRu /NPC catalyst demonstrated in Figure 3d. In addition to
macro meso micro
mechanistic advantages, this design also offers expanding feasibility. The pore-selective filling
strategy, relying on capillary infiltration and solvent immiscibility, is also experimentally validated
on non-carbon porous matrices (e.g., hierarchical porous Al O , Supplementary Figures 50-52).
2 3
However, when the support is changed to Al O , an unsatisfied catalytic performance is presented
2 3
(Supplementary Figure 53), mainly due to its irreplaceable function of carbon material as support
for activating acetylene.51 Furthermore, the lack of nitrogen-based metal coordination in Al O
2 3
fundamentally determines the different catalytic behavior. Thus, the non-carbon material confined
tandem catalysts may be more suitable in other reactions, which will be explored in future work.
As an attempt for the practical applications, an industrial side-line test using an ultra-low-loading
Ru -CuRu -AuRu /NPC (total metal loading 0.1 wt.%) sustained ~99.3% acetylene
macro meso micro
conversion and >99.5% VCM selectivity over ~1200 h (Supplementary Figure 54). Ultra-low coke
(2.36 wt.%, Supplementary Figure 55) was generated, demonstrating that the built-in tandem
architecture is durable and scalable under realistic operating conditions. Together with the techno-
economic evaluation in Supplementary Table 12, which shows a >16% reduction in catalyst-
related cost per ton of VCM compared with the HgCl /AC benchmark. These results underscore
2
the practical feasibility of the hierarchical tandem system.

In summary, we have established a built-in tandem catalysis platform based on a hierarchical
Ru -CuRu -AuRu /NPC architecture, in which Ru, CuRu and AuRu are selectively
macro meso micro
confined in macropores, mesopores and micropores via a capillarity-driven sequential pore-filling
strategy. Guided by a differential adsorption-energy descriptor, ΔE = E (C H )-E (VCM),
ads ads 2 2 ads
this pore-resolved arrangement overcomes competitive adsorption in VCM-rich environments and
drives acetylene conversion to near its thermodynamic limit, while maintaining >99.3%
conversion over 1200 h on stream at metal loading down to 0.1 wt.%. Mechanistic analysis reveals
a catalytic pathway sequentially connected within pores, involving three steps: ethylene-dichloride
dehydrochlorination, free radical reactions, and acetylene hydrochlorination. By integrating
hierarchical mass transport, site-specific chemistry and economical noble-metal usage within a
single porous reactor, this strategy provides a general blueprint for translating multistep vinyl-
chloride synthesis into single-catalyst tandem reactors.

Methods
Catalyst preparation. All metal-based catalysts were synthesized by a sequential pore-filling
incipient wetness impregnation followed by programmed decomposition. Taking Ru -
macro
CuRu -AuRu /NPC as an example: Au and Ru precursors (HAuCl , RuCl ) were dissolved
meso micro 4 3
in ionic liquid [BMIM+-Cl-] and introduced into the NPC micropores (1.0 wt.% Au, 0.5 wt.% Ru,
loading matched to the derived micropore volume, see Supplementary Figure 15), which was then
decomposed at 587 K. The micropores were temporarily blocked with ionic liquid [BMIM+-Tf₂N-].
Subsequently, Cu and Ru precursors (CuCl , RuCl ) were introduced into the mesopores (0.3
2 3
wt.% Cu, 0.5 wt.% Ru, matched to the mesopore volume) and decomposed at 587 K, followed by
mesopore blocking with [BMIM+-Tf₂N-]. Finally, RuCl in [BMIM+-Cl-] was introduced into the
3
macropores (0.5 wt.% Ru, matched to the macropore volume) and calcined at 776 K, fully
decomposing both ionic liquids, and yielding the Ru -CuRu -AuRu /NPC catalyst.
macro meso micro
Further details on the catalyst synthesis (including the preparation of single- and dual-pore-
confined references and the ultra-low-loading Ru -CuRu -AuRu /NPC catalyst, total
macro meso micro
metal loading 0.1 wt.%) and the preparation of the supports are provided in the Supplementary
Experimental 1.1 Catalyst preparation.

Catalyst characterization. The pore structure of the materials was analyzed using nitrogen
adsorption-desorption isotherms at 77 K with a Micromeritics Tristar II 3020 apparatus and
mercury porosimetry with a Quantachrome PM-3310 apparatus. Thermogravimetric analyses
(TGA) were performed with a Mettler Toledo TGA/DSC instrument. Focused ion beam-scanning
electron microscopy (FIB-SEM) was performed on a FEI Helios NanoLab 650 microscope. The
atomic-resolution structure was characterized by a JEOL JEM-ARM 200 F aberration-corrected
scanning transmission electron microscopy (AC-STEM). Energy dispersive X-ray (EDX)
spectroscopy was operated on a Tecnai G2 F30 S-Twin. Temperature-programmed desorption
(TPD) was measured on an Omnistar GSD320 mass spectrometer. Electron spin resonance (ESR)
spectroscopy was performed using a JES FA200 X-band ESR spectrometer. X-ray absorption fine
structure (XAFS) was performed at BL14W1 beamline of Shanghai Synchrotron Radiation
Facility (SSRF).

Computational details. Density functional theory (DFT) calculations were performed utilizing
the Vienna Ab initio simulation package (VASP-5.4) code. The Perdew-Becke-Ernzerhof
functional (PBE) was employed with inner electrons represented as projector augmented waves
(PAW). The valence monoelectronic states expanded as plane waves with a cutoff kinetic energy
of 450 eV. Dispersion contributions were introduced through the D3 approach. Relaxation was
allowed in the top two layers and followed by 20 Å of vacuum. The k-points sampling was a Γ-
centered 3×3×1 grid. A dipole correction was employed along the z direction. The climbing
nudged elastic band (CI-NEB) method was performed to confirm the transition state structures. In
all cases, the optimization thresholds were 10-5 and 10-4 eV for electronic and ionic relaxations,
respectively. The computational details are shown in the Supplementary Experimental 1.2
Computational details.

Catalytic evaluation. Ethylene-dichloride and acetylene cascade (EAC) was performed in a fixed-
bed micro-reactor using ethylene-dichloride (EDC) and acetylene (C H ) as the reactants
2 2
(Supplementary Figure 1). Before the reaction, the reactor was swept by N at 573 K (unless stated
2
otherwise) for 1 h to remove air and moisture. Then the gas was switched to the composition of
EDC and C H (molar ratio of EDC/C H is 1:1). The outlet gas was washed by NaOH solution (2
2 2 2 2
M, Sinopharm) to remove the unreacted HCl, and then analyzed by a gas chromatography (Fuli
GC9790) with a hydrogen flame ionization detector (FID). All evaluation procedures are detailed
in the Supplementary Experimental 1.3 Catalyst evaluation.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This article reported that an advanced built-in tandem catalysis in hierarchical pores was successfully developed for a cascade reaction of ethylene-dichloride dehydrochlorination and acetylene hydrochlorination to produce vinyl chloride. Based on my review, I would recommend a major revision accordingly:\n1. Very critically, the type and calculation method whose results are presented in 4 are missing in the draft. Please clearly specify the DFT methods and compare with relevant studies\n2. Abstract is too wordy and void of key results. Revised accordingly\n3. In the ethylene-dichloride dehydrochlorination reaction, have authors considered the release of toxic chlorinated gaseous products, which might be a concern to the environment?\n4. Conduct an environmental impact assessment\n5. Elaborate more on the thermodynamically favorable and unfavorable pathways seen in Figure 4\n6. Authors should review the guidelines for authors of each journal and adjust the style of the article according to the defined standards.\n7. It would be beneficial to incorporate the provided references and to include a comprehensive review of past works within the introduction section:\nA- https://doi.org/10.1016/j.diamond.2022.109602\nB- https://doi.org/10.1016/j.ssc.2021.114440\n8. The entire text should be thoroughly reviewed to correct any typos and grammatical errors.", "reviewer_2": "This study reports a novel hierarchical porous carbon-confined catalyst, fabricated through a precise pore-selective filling strategy that spatially confines Ru, CuRu, and AuRu components within macropores, mesopores, and micropores, respectively. This design achieves highly efficient catalysis for the ethylene dichloride-acetylene cascade (EAC) reaction. Systematic experimental characterization and theoretical calculations elucidate the reaction mechanism, while demonstrating exceptional catalytic activity and stability. Although the catalyst design is innovative, several issues require clarification:\n1. Direct Visualization of Hierarchical Pore Filling\nRecommendation: It is strongly suggested to employ FIB-SEM (Focused Ion Beam-Scanning Electron Microscopy) or analogous high-resolution tomography techniques to provide direct evidence of the hierarchical pore filling. This would validate the spatial confinement strategy and enhance the credibility of the pore-specific metal localization claims.\n2. Verification of Radical Pathway\nRecommendation: The manuscript proposes that the radical pathway exhibits the lowest activation energy barrier. To substantiate this claim, in situ infrared spectroscopy (e.g., DRIFTS) or spin-trapping ESR should be utilized to directly detect transient radical intermediates. Such data would provide critical experimental support for the proposed mechanism.\n3. Industrial Relevance and Cost Analysis\nConcern: Current industrial VCM production employs Ru- or Au-based catalysts with noble metal loadings as low as 0.1 wt.%. The reported total metal loading of 0.28 wt.% exceeds this benchmark.\nRecommendations:\n(i) Include catalytic performance data under ultra-low metal loading (≤0.1 wt.%) to align with industrial standards.\n(ii) Conduct a comprehensive cost-benefit analysis comparing the catalyst’s economic viability against conventional HgCl₂ or low-loading Ru/Au systems. Economic feasibility is a significant resistance to adoption.\n4. Data Rigor and Reproducibility\nConcern: Figures S28, S36, and S38 present limited data points, potentially compromising statistical reliability.\nRecommendation: All kinetic and thermodynamic plots (e.g., Arrhenius curves, sensitivity analyses) must include ≥5 data points per series to ensure scientific rigor, reproducibility, and adherence to best practices in catalysis research.", "reviewer_3": "Review of the Paper “Built-in Tandem Catalysis in Hierarchical Pores for Efficient Vinyl Chloride Production”\nI. Innovation Points\n(I) Catalytic System Design: Breaking the Spatial and Efficiency Bottlenecks of Traditional Tandem Catalysis\n1. Innovation of the \"Built-in Tandem Catalysis in Hierarchical Pores\" Concept. For the ethylene-dichloride (EDC)-acetylene cascade (EAC) reaction in traditional vinyl chloride (VCM) production, multiple reactors or layered catalyst beds are usually required. This study proposes, for the first time, a \"built-in tandem\" system where different active components are precisely confined in hierarchical pores (macropores, mesopores, and micropores). Using nitrogen-doped carbon (NPC) as the support, Ru, CuRu, and AuRu are immobilized in macropores, mesopores, and micropores respectively via a selective pore-filling strategy. This design enables the reaction to proceed orderly inside a single catalyst following the \"pore flow direction\", greatly shortening the diffusion path of intermediates and solving the efficiency loss caused by the \"macro-separation\" of traditional tandem systems.\n2. Precise Matching Between Active Components and Pore Functions: Based on the reaction mechanism and mass transfer characteristics, \"directional adaptation\" between active components and pore functions is achieved:\n- Macropore-confined Ru: Responsible for the dehydrochlorination of EDC, generating VCM, HCl, and free radicals;\n- Mesopore-confined CuRu: Catalyzes the addition reaction between free radicals and acetylene by virtue of its strong acetylene adsorption capacity;\n- Micropore-confined AuRu: Efficiently completes the hydrochlorination of residual acetylene.\nThis design not only avoids the competitive adsorption of VCM and acetylene (both with similar π-conjugated structures) on a single active site but also ensures the complete conversion of acetylene even under high VCM concentration through the \"gradient adsorption capacity\" (AuRu > CuRu > Ru). Ultimately, the acetylene conversion rate approaches the thermodynamic limit (99.3%, with a theoretical limit of 99.8%).\n(II) Preparation Method: Realizing Pore-Selective Confinement of Active Components\nStepwise Filling Strategy Based on Capillary Force and Solvent Immiscibility: To address the size differences of hierarchical pores (macropores, mesopores, and micropores), a preparation process of \"sacrificial solvent protection - selective impregnation - stepwise calcination\" is designed:\n1. First, the AuRu precursor is loaded using an ionic liquid (IL4) with a volume matching the micropore volume, followed by calcination;\n2. Then, the micropores are protected with an immiscible sacrificial solvent (IL3), and CuRu is loaded using IL4 with a volume matching the mesopore volume;\n3. Finally, the mesopores are protected, and Ru is filled in the macropores.\nThis strategy ultimately achieves the \"zero-crosstalk\" distribution of the three active components in different pores.\nII. Shortcomings\n1. The preparation of the catalyst in the paper relies on the \"selective pore-filling strategy\", which is based on the principles of capillary force and solvent immiscibility. It requires three steps to precisely confine Ru, CuRu, and AuRu in macropores, mesopores, and micropores. Additionally, the volume matching between the solvent and pores must be strictly controlled in each step (e.g., ~20 vol.% solvent to saturate micropores, ~50 vol.% to block mesopores). However, in practical applications, this process faces two core issues:\n- Problem of Uniformity in Pore Filling: During small-batch laboratory preparation, the pore structure (pore size distribution, pore volume) of the NPC support can be precisely controlled. However, in the scale production of industrial-grade supports, fluctuations in carbon source carbonization processes (e.g., dosage of ionic liquid template, distribution of calcination temperature) easily lead to non-uniform pore structures. Meanwhile, the uniformity of solvent spraying/penetration during stepwise impregnation is difficult to ensure, which may result in \"unfilled pores\" or \"cross-pore crosstalk of active components\" (e.g., Ru accidentally entering mesopores) in some supports, directly reducing catalytic activity and batch stability.\n- Insufficient Verification of Reproducibility and Universality in Catalyst Preparation: Although the paper mentions the feasibility of the \"selective pore-filling strategy\" on Al₂O₃ supports, it does not provide catalytic performance data of the catalyst on this support, making it impossible to prove the universality of the strategy for different supports. Additionally, the specific calculation method for \"volume matching between solvent and pores\" (e.g., how to accurately measure micropore volume to determine the dosage of IL4) and the recovery and recycling schemes for ionic liquids (IL3, IL4) are not mentioned. If IL3/IL4 cannot be recycled, the preparation cost will increase, limiting large-scale application.\n3. Lack of Direct Characterization for the Spatial Distribution of Active Components in Hierarchical Pores: Existing characterization methods (e.g., HAADF-STEM) can only observe the structure of active components in single-pore catalysts (e.g., macropore-only Ruₘₐcᵣₒ/NPC), but cannot directly prove the spatial distribution of \"three active components located in macropores, mesopores, and micropores respectively within the same catalyst\" (due to the disordered structure of hierarchical pores, it is difficult to achieve atomic-resolution overall imaging). Although indirect inference is made through XAS coordination environment analysis and single-pore reference samples, direct evidence (e.g., three-dimensional distribution characterization by focused ion beam scanning electron microscopy (FIB-SEM) combined with elemental mapping) is lacking, which may lead to disputes over the structural confirmation of \"pore-selective confinement\".\n4. Lack of Comprehensive Comparison with Existing Industrial Catalysts: The paper only compares the prepared catalyst with \"physical mixing systems\" and \"single-active-component systems\", but not with high-performance mercury-free catalysts that have been industrially applied or reported in recent years in terms of key indicators (e.g., space velocity tolerance, temperature window, HCl utilization rate, by-product selectivity). For example, in industrial EAC reactions, trace impurities in raw materials (e.g., H₂S, CO) may affect the reaction, but the paper does not investigate the inhibitory effect of impurities on catalyst activity, making it impossible to confirm its applicability in actual industrial raw materials. Moreover, the catalytic performance evaluation in the paper is mainly conducted under fixed experimental conditions (e.g., temperature of 573 K, EDC/C₂H₂ molar ratio of 1:1), and the influence of reaction parameter fluctuations (e.g., temperature variation, raw material ratio change) on catalytic performance is not investigated. For instance, local temperature fluctuations may occur in industrial reactors due to the different thermal effects of EDC dehydrochlorination (endothermic) and acetylene hydrochlorination (exothermic), but the paper does not study the catalyst stability under temperature gradients. Additionally, the influence of catalyst shaping processes (e.g., industrial production requires forming into particles or honeycombs) on pore structure and mass transfer efficiency is not mentioned, making it difficult to directly connect with industrial applications.\n5. Although the paper emphasizes that the catalyst has a \"total metal loading of only 0.28 wt.%\" and a stability of 700 hours, its industrial application still faces economic bottlenecks:\n- Procurement and Recovery Costs of Precious Metals: The catalyst contains two precious metals (Au and Ru). Although the loading is low, large-scale industrial production requires a huge amount of catalysts (e.g., a 10,000-ton VCM plant requires dozens of tons of catalysts), resulting in high procurement costs for precious metals. Meanwhile, the paper does not mention the recovery process of precious metals from spent catalysts. If precious metals cannot be recovered, it will not only cause resource waste but also increase the cost of solid waste treatment, weakening the market competitiveness of the technology.\n6. The paper only verifies the catalyst stability within 700 hours (acetylene conversion rate maintained at ~99.3%), but industrial catalysts need to operate continuously for thousands of hours and must cope with issues such as coking, active component loss, and bed pressure drop change. The paper points out that hierarchical pores can reduce coking, but it does not quantitatively analyze the coke content of the catalyst after 700 hours (e.g., measuring coke rate via thermogravimetric analysis (TGA)). In industrial production, reactants (especially acetylene) may undergo polymerization reactions to form coke when in long-term contact with active sites. If coke adheres to micropore AuRu sites or blocks mesopore channels, it will lead to a decrease in acetylene adsorption capacity and hindered intermediate transfer, eventually causing catalyst deactivation.\nIII. Conclusion\nThe paper is not recommended for publishing in nature communication."}, "author_response": "Dear Editor and Reviewers,\nIt is appreciated for the opportunity to revise our manuscript entitled “Built-in Tandem Catalysis in Hierarchical Pores for Efficient Vinyl Chloride Production”. (Manuscript ID: NCOMMS-25-74615). We have studied the valuable comments from the reviewers carefully, and tried our best to revise the manuscript. Attached please find the revised manuscript for your kind consideration. The point-to-point responses to the comments are listed as following:\nComments in blue - Reponse in black - Emphasis in bold\nIndicated figures and page numbers refer to the revised manuscript with changes highlighted.\nReviwers' comments:\nReviewer #1:\n1. This article reported that an advanced built-in tandem catalysis in hierarchical pores was successfully developed for a cascade reaction of ethylene-dichloride dehydrochlorination and acetylene hydrochlorination to produce vinyl chloride.\nBased on my review, I would recommend a major revision accordingly: Very critically, the type and calculation method whose results are presented in 4 are missing in the draft. Please clearly specify the DFT methods and compare with relevant studies.\nResponse: We appreciate the reviewer’s suggestion and have revised the manuscript to clarify the theoretical methodology underlying Figure 4 and to relate it more explicitly to previous DFT studies.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n(i) Specification of DFT methods.\nWe have added a dedicated subsection “Computational detail” in the manuscript and Supporting Information, where the full setup of the calculations used for Figures 3-4 is now described. In brief, all adsorption and reaction energies were obtained using the Vienna Ab initio Simulation Package (VASP) with the PBE exchange–correlation functional, PAW pseudopotentials, a plane-wave cutoff energy of 450 eV, and Grimme’s D3 dispersion correction. Slab models with a 20 Å vacuum layer and a Γ-centered 3×3×1 k-point mesh was used, with the top two layers relaxed. Transition states were located and confirmed using the climbing nudged elastic band (CI-NEB) method. We also explicitly define in this subsection how the reaction energy (ΔE), activation energy (E ), and adsorption energy (E ) are computed from a ads the energies of the initial, transition, and final states. These details now make clear the DFT protocol used for the generation of all energetics discussed in Figure 4.\n(ii) Comparison with relevant DFT literature.\nFollowing the reviewer’s recommendation:\nA- https://doi.org/10.1016/j.diamond.2022.109602;\nB- https://doi.org/10.1016/j.ssc.2021.114440.,\nWe have carefully read and cited recent DFT studies on vinyl chloride adsorption over nanostructured materials, including BN-based and SiC-based nanotubes (now cited as refs. 17–19). These works employ hybrid functionals such as B3LYP-D3(GD3BJ), PBE0, M06-2X, and ωB97XD together with a 6-311G(d) basis set to compute VCM adsorption energies in the range of ca. −0.1 to −0.8 eV, and they NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nshow that VCM adsorption strength is highly sensitive to substrate composition and electronic structure (e.g., Al/Ga or Ge doping enhances |E | and modifies the DOS ads and HOMO–LUMO gap). This conclusion is now explicitly mentioned in the Introduction as: “Recent density functional theory (DFT) works have also demonstrated that the adsorption of VCM and related small molecules is highly sensitive to surface composition and electronic structure.17–19”\nOur study is complementary in that we use periodic PBE-D3 slab models for Ru, CuRu and AuRu interfacial sites that are representative of working catalysts, and we focus on relative adsorption energies of C H vs. VCM and on full reaction pathways 2 2 for the EAC sequence. Nevertheless, the qualitative trends are consistent: tuning the local electronic structure of the active site (through alloying Ru with Cu or Au and through coordination to N-doped carbon) systematically modulates E (VCM) and ads the descriptor ΔE = E (C₂H₂) − E (VCM) (Figure 3b and Supplementary Figures ads ads ads S16-S25), in line with the sensitivity to composition reported in refs. 17-19. We have added this discussion to the text to better connect our calculations with the existing theoretical literature.\nWe hope that these additions adequately address the reviewer’s concern regarding the DFT methodology and its relation to previous studies.\nActions in the Supporting Information regarding the computational details: Page 7.\n1.2.2 Computational details\nDensity functional theory (DFT) calculations were performed utilizing the Vienna Ab initio simulation package (VASP) code. The Perdew-Becke-Ernzerhof functional NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n(PBE) was employed with inner electrons represented as projector augmented waves (PAW). The valence monoelectronic states expanded as plane waves with a cutoff kinetic energy of 450 eV. Dispersion contributions were introduced through the D3 approach. Relaxation was allowed in the top two layers and followed by 20 Å of vacuum. The k-points sampling was a Γ-centered 3×3×1 grid. A dipole correction was employed along the z direction. The climbing nudged elastic band (CI-NEB) method was performed to confirm the transition state structures. In all cases, the optimization thresholds were 10-5 and 10-4 eV for electronic and ionic relaxations, respectively.\nThe reaction energy (ΔE) and activation (E ) energy were calculated by the a Born-Oppenheimer energy difference between IS, TS, and FS:\nΔE = E - E ; E = E - E\nFS IS a TS IS\nwhere E , E , and E are the energies of IS, TS, and FS, respectively, and the IS TS FS\nequation for calculating E is given, as follows:\nads\nE = E - E - E\nads total substrate adsorbate\nwhere E , E , and E are the total energies of the substrate and adsorbate, total substrate adsorbate\nthe energy of the substrate, and that of the adsorbate, respectively.\n2. Abstract is too wordy and void of key results. Revised accordingly.\nResponse: We thank the reviewer for this valuable suggestion. In the revised manuscript, the Abstract has been completely rewritten to be more concise and to emphasize the key quantitative results of this work.\nThe revised Abstract is given below: “Tandem catalysis over disparate active sites is frequently designed to promote the catalytic efficiency for industrial reactions. NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nHerein, a built-in tandem system in a single hierarchical porous catalyst is constructed for vinyl chloride production from ethylene dichloride and acetylene cascade. Using a pore-selective filling strategy, Ru, CuRu, and AuRu components are sequentially confined in the macro-, meso- and micropores of carbon material. Mechanism study shows that ethylene-dichloride dehydrochlorination occurs on macropore Ru sites, generating vinyl chloride. H and Cl radicals react with acetylene on mesopore CuRu sites, and the residual acetylene is hydrochlorinated over micropore AuRu sites. The stronger acetylene adsorption of CuRu and AuRu in a VCM-rich atmosphere enables acetylene conversion near the thermodynamic limit and stable operation for 1200 h on stream. This built-in tandem catalysis in hierarchical pores provides a general paradigm for cascade reactions in a single porous catalyst.”\n3. In the ethylene-dichloride dehydrochlorination reaction, have authors considered the release of toxic chlorinated gaseous products, which might be a concern to the environment? Conduct an environmental impact assessment.\nResponse: We appreciate the reviewer’s concern regarding possible emissions of toxic chlorinated gases. We have now clarified both the product distribution and gas-phase emissions during EDC dehydrochlorination and EAC operation, and the broader environmental implications of replacing the industrial HgCl /AC catalyst by 2 the present Ru -CuRu -AuRu /NPC system.\nmacro meso micro\n(i) Selectivity and gaseous chlorinated products.\nIn our tandem EAC system, the only intended chlorinated product is vinyl chloride monomer (VCM). The reaction is conducted under O ‐free, strongly reducing 2 NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nconditions, which disfavors the formation of oxy-chlorinated species and higher chlorinated organics. In line with previous reports on acetylene hydrochlorination and EDC–acetylene cascade processes (React. Chem. Eng., 2018, 3, 34-40; Chinese Journal of Catalysis, 2022, 43, 820-831; Catal. Sci. Technol., 2016, 6, 1402-1409; Ind. Eng. Chem. Res., 2019, 58, 5404-5413.), which typically report VCM selectivities >99%. We observe VCM selectivities of ~99.5% throughout our tests.\nOnline GC analysis of the reactor effluent (both in laboratory tests and in the industrial side-line unit) shows that chlorinated carbon species other than VCM are only produced at trace levels, well within the carbon balance uncertainty and below the detection limit threshold of our analytical setup. In other words, the built-in tandem catalyst does not introduce additional families of toxic chlorinated gaseous products compared with existing VCM technologies. The gaseous chlorine inventory is essentially limited to VCM and HCl, which are already routinely managed in commercial plants.\n(ii) Industrial side-line long-term test.\nTo further verify the robustness and emission profile under realistic conditions, we carried out a side-line evaluation in an operating VCM plant. A slipstream of the industrial EDC–C H feed was passed through a fixed-bed reactor loaded with 2 2\nRu -CuRu -AuRu /NPC. As shown in the new Supplementary Figure S43, macro meso micro\nthe catalyst was operated for 1200 h in total (~1100 h on-stream, interrupted by five shutdowns). During this period, the total flow rate (60–200 mL min⁻¹), GHSV total (36-120 h-1), axial bed temperatures (upper/middle/bottom), and C H conversion 2 2 NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nwere continuously monitored. The C H conversion was stably maintained above 2 2 99.3%, very close to the thermodynamic limit, and the VCM selectivity remained ~99.5% over the entire campaign. No additional chlorinated gaseous species beyond those typical of standard VCM operation were detected in the vent stream. These results indicate that the tandem catalyst operates within the usual emission envelope of industrial VCM processes while offering higher efficiency and stability.\n)\nw mi\nn180\nFl\no\nm\nL/1\n6\n2\n0\n(\nH\nm 120S\no V\nott K ) 60 ( h\n,\nb\ndl\ne\nm\np. (\n5\n5\n6\n8\n0\n0\n0\n)\n-1\nmi d -t e 540 C\n,\ne\nrB e\nd\nfive shutdown events\n1002\nU p p 1st 2nd 3rd 4th 5th 99 C o n\n98\n.\n(\n0 200 400 600 800 1000 1200 %\n)\nTime on stream (h)\nSupplementary Figure S43. Industrial side-line long-term test of\nRu -CuRu -AuRu /NPC. Total metal loading: 0.1 wt.%. Reaction conditions: Gaseous macro meso micro\nflow = 60 - 200 mL/min, V = 100 mL, 520 – 540 K.\nCat\n(iii) Environmental assessment.\nIn addition, and in response to the reviewer’s request, we have carried out a techno-economic analysis that explicitly incorporates an environmental hazard/disposal term, comparing the present hierarchical\nRu -CuRu -AuRu /NPC catalyst with the benchmark HgCl /AC system macro meso micro 2 (Supplementary Table S11). Because HgCl /AC typically contains ≥10 wt% Hg, it 2 must be treated as hazardous waste, incurring an environmental disposal cost of ~15–20 USD kg⁻¹ catalyst. In contrast, the carbon-based NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nRu -CuRu -AuRu /NPC catalyst contains no toxic heavy metals, so its macro meso micro\ndisposal cost is negligible, and Au/Ru can be recovered or reused. After including these factors, the hierarchical tandem catalyst achieves a catalyst-related cost of~25–28 USD per ton of VCM, compared with ≥30–35 USD per ton for the Hg-based system, while completely eliminating mercury emissions and Hg-containing waste streams.\nSupplementary Table S11. Techno-economic comparison of HgCl /AC vs.\nmacro meso micro\nItem HgCl /AC Ru -CuRu -AuRu /NPC\n2 macro meso micro\nMetal loading a\n10 0.1\n(wt.%)\nCatalyst cost b\n≥ 15 ~ 80\n(USD/kg-catalyst)\nCatalyst operational VCM\nproductivity c 1 × (baseline) > 2 ×\n(normalized)\nCatalyst cost normalized to\nVCM output d ≥ 15 ≤ 40\n(USD/t-VCM)\nEnvironmental hazard /\ndisposal cost e 15–20 ~ 0\n(USD/kg)\nProcess advantage of EDC +\nC₂H₂ tandem pathway f 0 –10 (savings)\n(USD/t-VCM)\n~ 0\nPrecious-metal recovery credit\n(treated as\ng –15 to –20\nhazardous\n(USD/kg-catalyst)\nwaste)\nCatalyst cost after metal\nrecovery h ≥ 30–35 60 – 65\n(USD/kg)\nFinal total cost per ton VCM i\n≥ 30–35 ~ 25–28\n(USD/t)\na Metal loading. HgCl /AC typically contains ≥10 wt.% Hg (elemental basis).\nmacro meso micro\nb Catalyst cost. Computed based on the average market price over the past five years (Hg ≈ 0.03\nUSD/g, Au ≈ 62 USD/g, Ru ≈ 15 USD/g, Cu ≈ 0.0083 USD/g, IL3-4 ≈ 10–30 USD·kg⁻¹).\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nc Productivity normalization. The EDC + C₂H₂ cascade produces 2 mol VCM per cycle, vs. 1 mol\nVCM in the Hg-based single-step acetylene hydrochlorination.\nd Cost per ton VCM. Catalyst cost normalized by VCM productivity. High activity and >2×\ncapacity means Ru -CuRu -AuRu /NPC requires much less catalyst per unit VCM.\nmacro meso micro\ne Environmental disposal cost. Hg catalysts demand hazardous waste treatment (≥15–20 USD/kg).\nNPC-based catalyst contains no toxic metals, negligible disposal cost.\nf Process advantage of tandem reaction. EAC eliminates additional separation steps and the second\nreactor, at least 10 USD/t-VCM savings (conservative).\ng Recovery credit. Au and Ru prices are taken from current market data. ≥90 % recovery of Au/Ru\nby [AlCl₄]⁻-based ionic-liquid leaching (Ref. ACS Omega 2023,8, 8341−8345) is assumed, and\nthe corresponding metal-recovery credit is included in the net catalyst cost.\nh Net catalyst cost. Hg remains ≥30–35 after disposal; Ru–CuRu–AuRu falls to approx. 60–65\nUSD/kg after metal recovery.\ni Final cost per ton VCM. After combining catalyst cost normalization, process advantage and\nmetal recovery: HgCl /AC ≥ 30–35 USD/t, Ru -CuRu -AuRu /NPC ~ 25–28 USD/t.\n2 macro meso micro\nThus, from an environmental standpoint, the proposed built-in tandem system avoids the using of toxic mercury, maintains very high selectivity to VCM. A full life-cycle assessment is beyond the scope of this work, but our combined selectivity data, long-term industrial side-line test, and techno-economic analysis collectively demonstrate that the hierarchical Ru -CuRu -AuRu /NPC catalyst can reduce macro meso micro\nboth the environmental hazard and the catalyst-related cost per ton of VCM relative to current HgCl /AC-based technologies.\nA new Supplementary Table S11 and accompanying paragraph have been added to quantify the techno-economic and environmental comparison between HgCl /AC and\nmacro meso micro\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nA short paragraph summarizing these environmental considerations has been included in the manuscript:\nPage 21, Lines 391-398: As an attempt for the practical applications, an industrial side-line test using an ultra-low-loading Ru -CuRu -AuRu /NPC (total metal macro meso micro\nloading 0.1 wt.%) sustained ~99.3% acetylene conversion and >99.5% VCM selectivity over ~1200 h (Figure S43). Ultra-low coke (2.36 wt.%, Figure S44) was generated, demonstrating that the built-in tandem architecture is durable and scalable under realistic operating conditions. Together with the techno-economic evaluation in Table S11, which shows a >16% reduction in catalyst-related cost per ton of VCM compared with the HgCl /AC benchmark. These results underscore the practical 2\nfeasibility of the hierarchical tandem system.\n4. Elaborate more on the thermodynamically favorable and unfavorable pathways seen in Figure 4.\nResponse: We thank the reviewer for this helpful suggestion. In the revised manuscript, we have rewriten the discussion around Figures 4a-b to explicitly distinguish the thermodynamically favorable and unfavorable pathways on each type of active site (Ru, CuRu, and AuRu) and to clarify why the sequence Ru → macro CuRu → AuRu is both kinetically and thermodynamically enforced. The meso micro\nmodified description is as follows.\nPages 16-20: Meanwhile, the formation of Cl* radicals was directly verified by electron spin resonance (ESR) measurements (Figure 4b inset), which shows characteristic radical signals as a function of time (Figure S31), consistent with NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nreported Cl* features.48,49 These results indicate partial HCl dissociation (HCl → Cl* + H*). Based on experimental results, the desorption of VCM and HCl (black lines, steps a-c in Figures 4a, 4b) and the generation of H* and Cl* were modeled (steps c-d for energies in Figures 4a and diagrams in 4b), following the thermodynamic trend with a lowest activation energy of 0.27 eV (inset black histogram in Figure 4a). The above reaction process is referred as the ‘EDC decomposition’ process in subsequent discussion.\nTo study the probability of other pathways occurring at the Ru site, three additional thermodynamically unfavorable pathways were calculated: the one-step reaction of acetylene and EDC (C H + EDC → 2VCM, yellow lines in Figure 4a), acetylene 2 2 hydrochlorination (C H + HCl → VCM, blue lines in Figure 4a), and the radical 2 2 reaction pathway (C H + Cl* + H* → VCM, red lines in Figure 4a). Detailed reaction 2 2 energies are listed in the under region of Figure 4a (thermodynamically favorable), while their diagrams are shown in Figures S32-S34. Among these routes, the minimum activation energy is the acetylene hydrochlorination pathway (0.51 eV, inset blue histogram in Figure 4a), which is significantly higher than that of the proposed EDC decomposition process (inset black route, 0.27 eV). Therefore, both theoretical calculations and experimental results confirm that the EDC decomposition is the only feasible pathway over the Ru site. The reaction intermediates generated at the Ru site can migrate to other porous sites, potentially triggering synergistic effects.\nCompared with EDC, acetylene exhibits stronger adsorption on mesoporous CuRu and microporous AuRu (Figure S29). Obviously, EDC decomposition is hindered if NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nthe sites are preferential adsorbed by acetylene. In addition, the conversion of EDC over the macroporous Ru site is 99.54%, and that of acetylene is 92% (Figure S35), which means that EDC was essentially completely converted at the Ru site, while the subsequent mesoporous and microporous sites are responsible for the residual acetylene conversion.\nThe extreme lack of EDC makes it impossible to trigger the one-step reaction of acetylene and EDC on CuRu and AuRu sites, supported by their extremely high activation energies (1.64, 2.51 eV, yellow lines/histograms in Figure 4a). For the mesoporous CuRu site, the radical pathways exhibit the lowest energy barrier of 0.41 eV (red lines in Figure 4a), which is lower than that of acetylene hydrochlorination pathway (0.45 eV) and one-step reaction of acetylene and EDC (1.64 eV). In contrast, acetylene hydrochlorination is favored over the AuRu site, (blue lines in Figure 4a), with an activation energy of 0.49 eV, lower than that of 1.20 eV for the radical pathways and 2.51 eV for the one-step reaction. These findings demonstrate that the lowest energy pathways catalyzed on mesoporous CuRu and microporous AuRu sites are radical reactions and acetylene hydrochlorination, respectively.\nImportantly, the sequential activation along the\nmacropore → mesopore → micropore is not arbitrary but thermodynamically enforced. Once EDC is fully reacted at macroporous Ru sites (99.54% conversion, Figure S35), its downstream concentration is nearly zero, making EDC-involving pathways on CuRu and AuRu sites both thermodynamically disallowed and kinetically prohibitive. DFT calculations reveal prohibitively high barriers for EAC on CuRu (1.64 eV) and NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nAuRu (2.51 eV) sites, and no appreciable EDC adsorption (Figure S29), thereby excluding reversed or randomized reaction sequences, such as micropore → mesopore → macropore. Further kinetic analysis reveals that multiple reaction pathways coexist owing to the different reaction orders of the reactants (Figure S36). The superior performance of the three-pore\nRu -CuRu -AuRu /NPC system over the two-pore configurations macro meso micro\nRu -CuRu /NPC and Ru -AuRu /NPC (Figure S37, S38) powerfully macro meso macro micro\nvalidates the feasibility of a tandem catalytic route through hierarchical pores. The guiding descriptor, ΔE = E (C H )-E (VCM), effectively identifies the active site ads ads 2 2 ads\nconfinement within pores, ensuring the tandem conversion of acetylene in mesopores and micropores. These findings validate the directionality and pore-function assignment of the built-in tandem system. Therefore, optimal reaction pathways have been identified (Figure 4b). Specifically, ethylene-dichloride first undergoes hydrogen chloride removal at the Ru site (steps a-c), followed by the generation of VCM and HCl (steps c-d). Part of the HCl is dissociated to H and Cl radicals (step d). These species migrate and engage in addition reactions with acetylene at the CuRu (steps e, f) and AuRu sites (steps i, j), ensuring minimal energy barriers for VCM production (steps g, h, k). At CuRu sites, acetylene reacts with radicals, while classical acetylene hydrochlorination occurs at AuRu sites.\n5. Authors should review the guidelines for authors of each journal and adjust the style of the article according to the defined standards.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nResponse: We thank the reviewer for this comment. We have carefully re-checked the journal’s “Instructions for Authors” and also examined several recently published articles in this journal. As exemplified by Ref. Nature Communications, (2025) 16:10727, and Ref. Nature Communications, (2025) 16:10722, both formats: (i) separate Results and Discussion sections and (ii) a combined Results and Discussion section, are currently used and conform to the journal style.\nGiven that our work strongly interweaves experimental observations with mechanistic interpretation, we have chosen to follow the latter format, i.e., a single Results and discussion section, which we believe presents the integrated narrative more clearly. In the revised manuscript, we have ensured that the section heading, and overall structure strictly follow the journal’s style.\nIn addition, we have cross-checked and adjusted other stylistic elements (title format, abstract length, reference style, figure and table captions, and Supplementary Information labeling) to be fully consistent with the current author guidelines.\n6. It would be beneficial to incorporate the provided references and to include a comprehensive review of past works within the introduction section:\nA- https://doi.org/10.1016/j.diamond.2022.109602\nB- https://doi.org/10.1016/j.ssc.2021.114440.\nResponse: We thank the reviewer for these helpful suggestions. In the revised Introduction, we have now cited the recommended works (Refs. 17-19) and briefly mentioned their relevance. These DFT studies show that vinyl chloride adsorption on doped carbon and boron nitride nanostructures is highly sensitive to surface NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\ncomposition and electronic structure, which is consistent with our focus on controlling VCM/C₂H₂ competitive adsorption by tailoring hierarchical metal sites. The following sentence has been added after the discussion of competitive adsorption between VCM and acetylene.\nPage 3, Lines 44-46: Recent density functional theory (DFT) works have also demonstrated that the adsorption of VCM and related small molecules is highly sensitive to surface composition and electronic structure.17-19\n(17) Mohammadi, M.D.; Abdullah, H.Y. Vinyl chloride adsorption onto the surface of pristine, Al-, and Ga-doped boron nitride nanotube: A DFT study. Solid State Communications 2021, 337, 114440. DOI: 10.1016/j.ssc.2021.114440.\n(18) Mohammadi, M.D.; Abdullah, H.Y.; Qadir, K.W.; Suvitha, A. Theoretical investigation of intermolecular interactions between CNT, SiCNT and SiCGeNT nanomaterials with vinyl chloride molecule: A DFT, NBO, NCI, and QTAIM study. Diamond & Related Materials 2023, 131, 109602. DOI: 10.1016/j.diamond.2022.109602.\n(19) Mohammadi, M.D.; Qadir, K.W.; Abdullah, H.Y. A density functional theory investigation of the adsorption of CH , CO, CO , H , H O, N , NH , NO, and NO on 4 2 2 2 2 3 2\nMg and Mg Zn clusters. Computational and Theoretical Chemistry 2025, 1248, 20 19\n115227. DOI: 10.1016/j.comptc.2025.115227.\n7. The entire text should be thoroughly reviewed to correct any typos and grammatical errors.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nResponse: We appreciate the reviewer’s remark. In response, we have carefully re-read the entire manuscript and the Supporting Information and corrected typographical mistakes, grammatical issues, and awkward expressions throughout.\nThe revised version has been jointly edited by all co-authors to improve clarity and readability. All corrections with changes highlighted have been implemented in the current manuscript.\nReviewer #2:\n1. This study reports a novel hierarchical porous carbon-confined catalyst, fabricated through a precise pore-selective filling strategy that spatially confines Ru, CuRu, and AuRu components within macropores, mesopores, and micropores, respectively. This design achieves highly efficient catalysis for the ethylene dichloride-acetylene cascade (EAC) reaction. Systematic experimental characterization and theoretical calculations elucidate the reaction mechanism, while demonstrating exceptional catalytic activity and stability. Although the catalyst design is innovative, several issues require clarification:\n1. Direct Visualization of Hierarchical Pore Filling\nRecommendation: It is strongly suggested to employ FIB-SEM (Focused Ion Beam-Scanning Electron Microscopy) or analogous high-resolution tomography techniques to provide direct evidence of the hierarchical pore filling. This would validate the spatial confinement strategy and enhance the credibility of the pore-specific metal localization claims.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nResponse: We thank the reviewer for this constructive suggestion. In the revised manuscript, we now provide direct cross-sectional visualization of the hierarchical pore filling by FIB-SEM combined with element-specific line-scan analysis, as shown in the updated Figure 2d in the revised manuscript.\nA cross section with a length of ca. 19.75 μm and a milling depth of 6.11 μm was prepared on a representative Ru -CuRu -AuRu /NPC catalyst (Figure 2-d1).\nmacro meso micro\nAlong this cross section, three characteristic pores can be seen: macropores, mesopores, and micropores. Elemental line scans across these regions (Figure 2-d2) clearly reveal pore-specific metal distributions. In the macropore region, a pronounced Ru signal is observed, whereas Cu and Au signals are essentially at background level, indicating that Ru species predominantly reside in macropores. In the mesopore region, both Cu and Ru signals are detected with comparable intensity, consistent with the presence of CuRu sites confined in mesopores. In contrast, the micropore-rich region displays strong Au and Ru signals but negligible Cu, demonstrating that AuRu sites are preferentially located in micropores.\nThese FIB-SEM/EDS results provide direct spatial evidence that Ru, CuRu and AuRu components are selectively confined in macro-, meso- and micropores, respectively, in excellent agreement with the stepwise pore-volume evolution, XAS coordination analysis and reference single-pore catalysts discussed in Figure 2a–c and Figures. S5–S15. We have revised the text around Figure 2d to highlight this new piece of evidence and to better articulate how it supports the capillarity-driven pore-selective filling strategy.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nPages 11, Lines 185-196: To further visualize the spatial distribution of metal species within the hierarchical pores, focused ion beam–scanning electron microscopy (FIB-SEM) was performed on Ru -CuRu -AuRu /NPC (Figure 2d). A cross macro meso micro\nsection with a length of ca. 19.75 μm and a milling depth of 6.11 μm was opened on a representative catalyst surface (Figure 2-d1), where macropores, mesopores and micropores are clearly observed, respectively. Elemental line-scan profiles across these regions (Figure 2-d2) show that Ru gives a dominant signal in the macropore region, while Cu and Au are nearly undetectable, indicating that Ru species mainly occupy macropores. In the mesopore region, both Cu and Ru are detected with comparable intensity, proving that CuRu sites are confined in mesopores. In contrast, the micropore-rich region exhibits strong Au and Ru signals with negligible Cu, evidencing the preferential location of AuRu sites in micropores. The FIB-SEM results may offer direct evidence for the catalyst location, sufficiently proving the efficacy of the capillarity-driven and the pore-selective filling strategy.\nFigure 2. Characterizations of hierarchical pores confined catalysts. (d1) FIB-SEM images and (d2) EDS profiles across the marked regions of Ru -CuRu -AuRu /NPC.\nmacro meso micro\n2. Verification of Radical Pathway\nRecommendation: The manuscript proposes that the radical pathway exhibits the lowest activation energy barrier. To substantiate this claim, in situ infrared NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nspectroscopy (e.g., DRIFTS) or spin-trapping ESR should be utilized to directly detect transient radical intermediates. Such data would provide critical experimental support for the proposed mechanism.\nResponse: We appreciate the reviewer’s suggestion to experimentally verify the radical pathway. In response, we have performed in ESR measurements under EDC decomposition conditions over the evaluated catalyst.\nAs shown in the newly added Figure S31, a characteristic ESR signal centered at ~3510 G (g ≈ 2.0) is clearly observed during the reaction proceeds from 2 to 20 min. This signal shape and g-value are consistent with Cl* radicals reported in the literature (J. Am. Chem. Soc. 2024, 146, 29441−29449), confirming that chlorine radicals are indeed generated during EDC dehydrochlorination. The time-resolved evolution of the signal demonstrates that these radicals are formed continuously under steady reaction conditions, which provides direct experimental evidence for the involvement of a radical pathway.\nWe have incorporated this new ESR dataset into the “Tandem catalysis mechanism” section and now explicitly correlate the observed Cl* radicals with the lowest-barrier radical route identified by DFT. Together with the kinetic analysis and theoretical energy profiles, the ESR results strongly support the proposed radical-mediated steps in the overall tandem mechanism.\nPages 16-17, Lines 307-310: Meanwhile, the formation of Cl* radicals was directly verified by electron spin resonance (ESR) measurements (Figure 4b inset), which shows characteristic radical signals as a function of time (Figure S31), consistent with NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nreported Cl* features.48,49 These results indicate partial HCl dissociation (HCl → Cl* + H*).\nSupplementary Figure S31. ESR spectra of Ru -CuRu -AuRu /NPC. Reaction macro meso micro\nconditions: GHSV = 10,000 h-1, 573 K, 20 vol.% C H , 20 vol.% EDC, 60 vol.% VCM.\nTotal 2 2\n3. Industrial Relevance and Cost Analysis\nConcern: Current industrial VCM production employs Ru- or Au-based catalysts with noble metal loadings as low as 0.1 wt.%. The reported total metal loading of 0.28 wt.% exceeds this benchmark.\nRecommendations:\n(i) Include catalytic performance data under ultra-low metal loading (≤0.1 wt.%) to align with industrial standards.\n(ii) Conduct a comprehensive cost-benefit analysis comparing the catalyst’s economic viability against conventional HgCl₂ or low-loading Ru/Au systems. Economic feasibility is a significant resistance to adoption.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nResponse: We thank the reviewer for this important comment regarding industrial relevance.\n(i) Ultra-low metal loading and catalytic performance.\nIn addition to the model catalyst used for mechanistic studies, we have prepared an industrial side-line formulation of Ru -CuRu -AuRu /NPC with a total metal macro meso micro\nloading of 0.1 wt.%. The long-term performance of this ultra-low-loading catalyst has been evaluated on an industrial side-line reactor and is now presented in Supplementary Figure S43. Under practical EDC+C H feeds, gaseous flow of 2 2\n60–200 mL min⁻¹ and a catalyst volume of 100 mL, the catalyst maintains >99.3% acetylene conversion and >99.5% VCM selectivity over ~1100 h on stream (total test time ~1200 h including five shutdown events). This demonstrates that the hierarchical tandem architecture remains highly active and stable even at a total metal loading that matches industrial benchmarks (0.1 wt.%).\n)\nw mi\nn180\nFl\no\nm\nL/12\n6\n0\n(\nH\nm 120S\no V\nott K ) 60 ( h\n,\nb\ndl\ne\nm\np. (\n5\n5\n6\n8\n0\n0\n0\n)\n-1\nmi d -t e 540 C\n,\ne\nrB e\nd\nfive shutdown events\n1002\nU p p 1st 2nd 3rd 4th 5th 99 C o n\n98\n.\n(\n0 200 400 600 800 1000 1200 %\n)\nTime on stream (h)\nSupplementary Figure S43. Industrial side-line long-term test of\nRu -CuRu -AuRu /NPC. Total metal loading: 0.1 wt.%. Reaction conditions: Gaseous macro meso micro\nflow = 60 - 200 mL/min, V = 100 mL, 520 – 540 K.\nCat\n(ii) Cost–benefit analysis.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nWe have carried out a techno-economic analysis that explicitly incorporates an environmental hazard/disposal term, comparing the present hierarchical\nRu -CuRu -AuRu /NPC catalyst with the benchmark HgCl /AC system macro meso micro 2 (Supplementary Table S11). The calculation integrates four components: (i) elemental metal loading multiplied by current market prices, (ii) catalyst productivity normalized to VCM yield, (iii) environmental and disposal penalties associated with mercury handling, and (iv) precious-metal recovery credit. After scaling the noble-metal formulation to a total loading of ~ 0.1 wt%, the catalyst cost of\nRu -CuRu -AuRu /NPC is calculated as ~ 60–65 USD·kg⁻¹, slightly higher macro meso micro\nthan the ≥30–35 USD·kg⁻¹ for HgCl₂/AC once hazardous-waste disposal is included. When normalized to VCM production, the hierarchical catalyst further benefits from its two-VCM-per-cycle stoichiometry and superior stability, reducing the overall cost to ~ 25–28 USD per ton of VCM, compared with ≥30–35 USD per ton for the Hg-based catalyst. These results demonstrate that, despite employing noble metals, the hierarchical catalyst delivers a >16% reduction in cost per ton of VCM while completely eliminating mercury emissions. This analysis highlights the practical industrial relevance of built-in tandem catalysis and underscores its potential as a sustainable replacement for Hg-based acetylene hydrochlorination technologies.\nSupplementary Table S11. Techno-economic comparison of HgCl /AC vs.\nmacro meso micro\nItem HgCl /AC Ru -CuRu -AuRu /NPC\n2 macro meso micro\nMetal loading a\n10 0.1\n(wt.%)\nCatalyst cost b\n≥ 15 ~ 80\n(USD/kg-catalyst)\nCatalyst operational VCM\nproductivity c 1 × (baseline) > 2 ×\n(normalized)\nCatalyst cost normalized to\nVCM output d ≥ 15 ≤ 40\n(USD/t-VCM)\nEnvironmental hazard /\ndisposal cost e 15–20 ~ 0\n(USD/kg)\nProcess advantage of EDC + 0 –10 (savings)\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nC₂H₂ tandem pathway f\n(USD/t-VCM)\n~ 0\nPrecious-metal recovery credit\n(treated as\ng –15 to –20\nhazardous\n(USD/kg-catalyst)\nwaste)\nCatalyst cost after metal\nrecovery h ≥ 30–35 60 – 65\n(USD/kg)\nFinal total cost per ton VCM i\n≥ 30–35 ~ 25–28\n(USD/t)\na Metal loading. HgCl /AC typically contains ≥10 wt.% Hg (elemental basis).\nmacro meso micro\nb Catalyst cost. Computed based on the average market price over the past five years (Hg ≈ 0.03\nUSD/g, Au ≈ 62 USD/g, Ru ≈ 15 USD/g, Cu ≈ 0.0083 USD/g, IL3-4 ≈ 10–30 USD·kg⁻¹).\nc Productivity normalization. The EDC + C₂H₂ cascade produces 2 mol VCM per cycle, vs. 1 mol\nVCM in the Hg-based single-step acetylene hydrochlorination.\nd Cost per ton VCM. Catalyst cost normalized by VCM productivity. High activity and >2×\ncapacity means Ru -CuRu -AuRu /NPC requires much less catalyst per unit VCM.\nmacro meso micro\ne Environmental disposal cost. Hg catalysts demand hazardous waste treatment (≥15–20 USD/kg).\nNPC-based catalyst contains no toxic metals, negligible disposal cost.\nf Process advantage of tandem reaction. EAC eliminates additional separation steps and the second\nreactor, at least 10 USD/t-VCM savings (conservative).\ng Recovery credit. Au and Ru prices are taken from current market data. ≥90 % recovery of Au/Ru\nby [AlCl₄]⁻-based ionic-liquid leaching (Ref. ACS Omega 2023,8, 8341−8345) is assumed, and\nthe corresponding metal-recovery credit is included in the net catalyst cost.\nh Net catalyst cost. Hg remains ≥30–35 after disposal; Ru–CuRu–AuRu falls to approx. 60–65\nUSD/kg after metal recovery.\ni Final cost per ton VCM. After combining catalyst cost normalization, process advantage and\nmetal recovery: HgCl /AC ≥ 30–35 USD/t, Ru -CuRu -AuRu /NPC ~ 25–28 USD/t.\n2 macro meso micro\nPage 21, Lines 391-398: As an attempt for the practical applications, an industrial side-line test using an ultra-low-loading Ru -CuRu -AuRu /NPC (total metal macro meso micro\nloading 0.1 wt.%) sustained ~99.3% acetylene conversion and >99.5% VCM selectivity over ~1200 h (Figure S43). Ultra-low coke (2.36 wt.%, Figure S44) was generated, demonstrating that the built-in tandem architecture is durable and scalable under realistic operating conditions. Together with the techno-economic evaluation in Table S11, which shows a >16% reduction in catalyst-related cost per ton of VCM NO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\ncompared with the HgCl /AC benchmark. These results underscore the practical 2\nfeasibility of the hierarchical tandem system.\n4. Data Rigor and Reproducibility\nConcern: Figures S28, S36, and S38 present limited data points, potentially compromising statistical reliability.\nRecommendation: All kinetic and thermodynamic plots (e.g., Arrhenius curves, sensitivity analyses) must include ≥5 data points per series to ensure scientific rigor, reproducibility, and adherence to best practices in catalysis research.\nResponse: Following the reviewer’s recommendation, we have revised all the kinetic Figures to display the full datasets with ≥5 data points in each series. The corresponding fitting parameters have also been added to the figure captions and Supplementary Tables. These updates confirm that the kinetic data are fully reproducible.\nActions in the Supporting Information:\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n2.10 2.15 2.20 2.25 2.30\nSupplementary Figure 2.2-6. TPD profiles of the evaluated NPC catalysts under different heating rate (β represents the heating rate of 4, 5, 6, 7, 8 and 9 K min-1, respectively). (a) EDC,\nH\n(b) C H . (c) Arrhenius plots of NPC catalyst with the corresponding desorption energy (E ) for\n2 2 d\nEDC (black balls) and C H (red balls).\n2 2\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\n).u.a(ytisnetnI\na b\n300 350 400 450 500 550 600 650 700\nc\nCH\n2 2\nE = 48 kJ/mol\nd\nE = 71 kJ/mol\nd\nEDC\n1000/T (K-1)\np\n).u.a(ytisnetnI\nEDC T p\nβ = 8 K/min 476 K H\nβ = 7 K/min\nβ = 6 K/min\nβ = 5 K/min\nH\nβ = 4 K/min\nH\n300 350 400 450 500 550 600 650 700\nTemperature (K)\n).u.a(ytisnetnI\nC 2 H 2 T p\nH\nβ = 6 K/min\nβ = 5 K/min\nβ = 4 K/min\nH\nTemperature (K)\nNature Communications\na R u - C u R u - A u R u /N P C b Ru /NPC + CuRu /NPC + AuRu /NPC\nmacro meso micro macro mecro micro\nT p β = 9 K/min 475 K T p β H = 9 K/min\nu.) 471 K β H = 8 K/min u.)\nI\nnte\nnsit u\n(a.\n45\n4\n8\n6 5\nK\nK β\nβ\nH\nH\n=\n=\n7\nK\n/\n/\nm\nm\ni\ni\nn\nn\nI\nnte\nnsit u\n(a.\n4\n4\n5\n6\n9\nK β\nβ\nH\nH\n=\n=\n7\nK\n/\n/\nm\nm\ni\ni\nn\nn\nβ = 5 K/min\nβ = 4 K/min\n300 350 400 450 500 550 600 650 700 300 350 400 450 500 550 600 650 700\nTemperature (K) Temperature (K)\nc AuRu -AuRu -AuRu /NPC\nmacro meso micro\nT\np\nu.) 481 K β H = 8 K/min\nnsit u\n(a.\nI\nnte\nβ\nH\n= 6 K/min\nβ = 4 K/min\nH\n300 350 400 450 500 550 600 650 700\nTemperature (K)\nSupplementary Figure S27. VCM-TPD profiles of the evaluated catalysts of: (a)\nRu -CuRu -AuRu /NPC, (b) Ru /NPC + CuRu /NPC + AuRu /NPC, and (c)\nmacro meso micro macro meso micro\nAuRu -AuRu -AuRu /NPC under different heating rate. β represents the program heating\nmacro meso micro H\nrate at 4, 5, 6, 7, 8 and 9 K/min, respectively.\nE = 32 kJ/mol\nd\nRu -CuRu -AuRu /NPC\nmacro meso micro\nu.)\nE = 37 kJ/mol\na. d\ny\n(\nnsit\ne\nnt\nI\nRu /NPC + CuRu /NPC + AuRu /NPC\nmacro mecro micro\nE = 48 kJ/mol\nd\nAuRu -AuRu -AuRu /NPC\nmacro meso micro\n2.05 2.10 2.15 2.20 2.25 2.30\n1000/T\np\n(K-1)\nSupplementary Figure S28. Arrhenius plots of Ru -CuRu -AuRu /NPC (black balls),\nmacro meso micro\nRu /NPC + CuRu /NPC + AuRu /NPC (green balls), and\nmacro meso micro\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nAuRu -AuRu -AuRu /NPC (red balls) catalysts with the corresponding desorption\nmacro meso micro\nenergy.\nEDC\nCH\n2 2\nn = 0.27\nn\nr\nl\nn = 0.11\n−5.4 −5.2 −5.0 −4.8 −4.6 −4.4 −4.2 −4.0\nln P\nEDC\n, P\nC2H2\n/ -\nSupplementary Figure S36. Reaction ratesas a function of the inlet partial pressure of EDC or\nC H for Ru -CuRu -AuRu /NPC catalyst. The partial reaction order of both reactants, n,\n2 2 macro meso micro\nis indicated by the slope of the grey fitting lines, respectively. Each point was obtained in a single\nexperiment after 30 min time-on-stream.\nn\nr\nl 53 kJ/mol\n1.68 1.70 1.72 1.74 1.76 1.78\n1000/T (K-1)\nSupplementary Figure S38. Arrhenius plot of Ru -CuRu -AuRu /NPC catalyst with the\nmacro meso micro\ncorresponding apparent activation energy, E . The apparent activation energy of\na\nRu -CuRu -AuRu /NPC is calculated to be 53 kJ/mol (~ 0.5 eV).\nmacro meso micro\nReviewer #3:\n1. Review of the Paper “Built-in Tandem Catalysis in Hierarchical Pores for Efficient\nVinyl Chloride Production”\nI. Innovation Points\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n(I) Catalytic System Design: Breaking the Spatial and Efficiency Bottlenecks of\nTraditional Tandem Catalysis\n1. Innovation of the \"Built-in Tandem Catalysis in Hierarchical Pores\" Concept. For\nthe ethylene-dichloride (EDC)-acetylene cascade (EAC) reaction in traditional vinyl\nchloride (VCM) production, multiple reactors or layered catalyst beds are usually\nrequired. This study proposes, for the first time, a \"built-in tandem\" system where\ndifferent active components are precisely confined in hierarchical pores (macropores,\nmesopores, and micropores). Using nitrogen-doped carbon (NPC) as the support, Ru,\nCuRu, and AuRu are immobilized in macropores, mesopores, and micropores\nrespectively via a selective pore-filling strategy. This design enables the reaction to\nproceed orderly inside a single catalyst following the \"pore flow direction\", greatly\nshortening the diffusion path of intermediates and solving the efficiency loss caused\nby the \"macro-separation\" of traditional tandem systems.\n2. Precise Matching Between Active Components and Pore Functions: Based on the\nreaction mechanism and mass transfer characteristics, \"directional adaptation\"\nbetween active components and pore functions is achieved:\n- Macropore-confined Ru: Responsible for the dehydrochlorination of EDC,\ngenerating VCM, HCl, and free radicals;\n- Mesopore-confined CuRu: Catalyzes the addition reaction between free radicals and\nacetylene by virtue of its strong acetylene adsorption capacity;\n- Micropore-confined AuRu: Efficiently completes the hydrochlorination of residual\nacetylene.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nThis design not only avoids the competitive adsorption of VCM and acetylene (both\nwith similar π-conjugated structures) on a single active site but also ensures the\ncomplete conversion of acetylene even under high VCM concentration through the\n\"gradient adsorption capacity\" (AuRu > CuRu > Ru). Ultimately, the acetylene\nconversion rate approaches the thermodynamic limit (99.3%, with a theoretical limit\nof 99.8%).\n(II) Preparation Method: Realizing Pore-Selective Confinement of Active\nComponents\nStepwise Filling Strategy Based on Capillary Force and Solvent Immiscibility: To\naddress the size differences of hierarchical pores (macropores, mesopores, and\nmicropores), a preparation process of \"sacrificial solvent protection - selective\nimpregnation - stepwise calcination\" is designed:\n1. First, the AuRu precursor is loaded using an ionic liquid (IL4) with a volume\nmatching the micropore volume, followed by calcination;\n2. Then, the micropores are protected with an immiscible sacrificial solvent (IL3),\nand CuRu is loaded using IL4 with a volume matching the mesopore volume;\n3. Finally, the mesopores are protected, and Ru is filled in the macropores.\nThis strategy ultimately achieves the \"zero-crosstalk\" distribution of the three active\ncomponents in different pores.\nResponse: We sincerely thank the reviewer for the very positive and insightful\nassessment of our work and for clearly articulating the key innovation points. We\nfully agree with the reviewer’s summary. In the revised manuscript we have slightly\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nrefined the Introduction and Results and discussion sections to more clearly highlight\nthese innovation points in line with the reviewer’s summary. We are grateful for the\nreviewer’s supportive comments.\n2. II. Shortcomings\n1. The preparation of the catalyst in the paper relies on the \"selective pore-filling strategy\", which is based on the principles of capillary force and solvent immiscibility.\nIt requires three steps to precisely confine Ru, CuRu, and AuRu in macropores,\nmesopores, and micropores. Additionally, the volume matching between the solvent\nand pores must be strictly controlled in each step (e.g., ~20 vol.% solvent to saturate\nmicropores, ~50 vol.% to block mesopores). However, in practical applications, this\nprocess faces two core issues:\n- Problem of Uniformity in Pore Filling: During small-batch laboratory preparation,\nthe pore structure (pore size distribution, pore volume) of the NPC support can be\nprecisely controlled. However, in the scale production of industrial-grade supports,\nfluctuations in carbon source carbonization processes (e.g., dosage of ionic liquid\ntemplate, distribution of calcination temperature) easily lead to non-uniform pore\nstructures. Meanwhile, the uniformity of solvent spraying/penetration during stepwise\nimpregnation is difficult to ensure, which may result in \"unfilled pores\" or\n\"cross-pore crosstalk of active components\" (e.g., Ru accidentally entering mesopores)\nin some supports, directly reducing catalytic activity and batch stability.\nResponse: We sincerely thank the reviewer for this very important comment. In the\nrevised manuscript we have added more detailed pore-structure characterization as a\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nfunction of ionic liquid (IL) loading, and we now more clearly describe how the\nfilling proceeds in practice and how robust it is.\n(i) Supplementary data clarifying the stepwise filling process.\nTo directly visualize the filling sequence, we combined N sorption (for micropores)\n2\nand mercury intrusion porosimetry (for meso- and macropores), following the strategy\nreported in Ref. Adsorption, 2011, 17: 561–571. The new measurements are presented\nin the Figure 2c and revised Supplementary Figure S7. The results show that, as the\nIL loading is increased: the micropore volume decreases continuously and becomes\nessentially saturated when the IL amount reaches ~20 vol.% of the total pore volume;\nthe mesopore volume is fully filled at ~50 vol.% IL (Figure S7); further increase in IL\nloading primarily reduces the macropore volume, indicating the onset of macropore\nfilling.\nThese results provide a quantitative description of the filling sequence and confirm\nthat, under our preparation conditions, the selective pore-filling strategy indeed\nproceeds in the intended order of micropores → mesopores → macropores, rather\nthan relying on an idealized assumption.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n0 50 100\nSupplementary Figure S7. Pore size distribution of NPC with distinct IL loading amounts from 0\nto 60 vol.%.\n(ii) Influence of local non-uniformity.\nThe values of “~20 vol.%” and “~50 vol.%” therefore represent the centres of\npractical operating windows, not knife-edge critical points that require perfect\nmatching for each particle. Within these windows, some degree of local\nnon-uniformity is inevitable: a fraction of pores may be only partially filled, and a\nsmall number of Ru sites may appear in mesopores. In such cases, the main effect is a\nmoderate change in local site density, while the global distribution of active\ncomponents still follows the designed hierarchy.\nThis conclusion is consistently supported by both bulk and local structural probes:\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\n).u.a(ytisnetnI\n0 50 100\nD (nm) D (nm)\n).u.a(ytisnetnI\na b\nNature Communications\ni) In the revised manuscript, we now provide direct cross-sectional visualization of\nthe hierarchical pore filling by FIB-SEM combined with element-specific line-scan\nanalysis, as shown in the new Figure 2d.\nA cross section with a length of ca. 19.75 μm and a milling depth of 6.11 μm was\nprepared on a representative Ru -CuRu -AuRu /NPC catalyst (Figure 2-d1).\nmacro meso micro\nAlong this cross section, three characteristic pores can be seen: macropores,\nmesopores, and micropores. Elemental line scans across these regions (Figure 2-d2)\nclearly reveal pore-specific metal distributions. In the macropore region, a\npronounced Ru signal is observed, whereas Cu and Au signals are essentially at\nbackground level, indicating that Ru species predominantly reside in macropores. In\nthe mesopore region, both Cu and Ru signals are detected with comparable intensity,\nconsistent with the presence of CuRu sites confined in mesopores. In contrast, the\nmicropore-rich region displays strong Au and Ru signals but negligible Cu,\ndemonstrating that AuRu sites are preferentially located in micropores.\nThese FIB-SEM/EDS results provide direct spatial evidence that Ru, CuRu and\nAuRu components are selectively confined in macro-, meso- and micropores,\nrespectively, in excellent agreement with the stepwise pore-volume evolution, XAS\ncoordination analysis and reference single-pore catalysts discussed in Figure 2a-c and\nFigures. S5-S15.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nFigure 2. Characterizations of hierarchical pores confined catalysts. (d1) FIB-SEM images and (d2)\nEDS profiles across the marked regions of Ru -CuRu -AuRu /NPC.\nmacro meso micro\nii) X-ray absorption spectroscopy (XANES/EXAFS) for Au, Ru, and Cu (Figure 2e\nand Figures S10–S13) is volume-averaging and shows dominant Au–N coordination\nfor Au, Cu–Ru/Cu–N environments for Cu, and Ru–N together with Ru–Ru/Ru–Cu\npaths for Ru, matching the targeted pore-specific configurations.\nTaken together, these data indicate that any “unfilled pores” or cross-pore\noccupation are statistically minor and do not overturn the overall assignment of Ru,\nCuRu, and AuRu to macro-, meso-, and micropores, respectively. Thus, their impact\non catalytic behaviour is limited.\nWe have revised the text around Figure 2d to highlight this new piece of evidence\nand to better articulate how it supports the capillarity-driven pore-selective filling strategy.\nPage 11, Lines 185-196: To further visualize the spatial distribution of metal species\nwithin the hierarchical pores, focused ion beam–scanning electron microscopy\n(FIB-SEM) was performed on Ru -CuRu -AuRu /NPC (Figure 2d). A cross macro meso micro\nsection with a length of ca. 19.75 μm and a milling depth of 6.11 μm was opened on a\nrepresentative catalyst surface (Figure 2-d1), where macropores, mesopores and\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nmicropores are clearly observed, respectively. Elemental line-scan profiles across\nthese regions (Figure 2-d2) show that Ru gives a dominant signal in the macropore\nregion, while Cu and Au are nearly undetectable, indicating that Ru species mainly\noccupy macropores. In the mesopore region, both Cu and Ru are detected with\ncomparable intensity, proving that CuRu sites are confined in mesopores. In contrast,\nthe micropore-rich region exhibits strong Au and Ru signals with negligible Cu,\nevidencing the preferential location of AuRu sites in micropores. The FIB-SEM\nresults may offer direct evidence for the catalyst location, sufficiently proving the\nefficacy of the capillarity-driven and the pore-selective filling strategy.\n(iii) Robust activity and batch stability of an ultra-low-loading industrial\nside-line catalyst.\nTo further address the reviewer’s concern that such non-uniformity might reduce\ncatalytic activity and batch-to-batch stability, we have also prepared an\nultra-low-loading industrial side-line formulation of Ru -CuRu -AuRu /NPC\nmacro meso micro\nwith a total metal loading of 0.1 wt.% using the same stepwise filling protocol on a\nlarger batch of NPC support. The performance of this catalyst is now presented in\nSupplementary Figure S43.\nUnder realistic EDC + C₂H₂ feeds, a gaseous flow of 60–200 mL min⁻¹ and a\ncatalyst volume of 100 mL, this ultra-low-loading catalyst maintains ~99.3%\nacetylene conversion, and >99.5% VCM selectivity over ~1100 h on stream (total test\ntime ~1200 h including five shutdowns). The fact that near-equilibrium activity and\nlong-term stability are preserved at 0.1 wt.% total metal loading under industrially\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nrelevant conditions demonstrates that the built-in tandem architecture is robust to the\nlevel of pore-structure variation and impregnation non-uniformity encountered in\npractice, and does not suffer from noticeable performance loss due to “unfilled pores”\nor local crosstalk.\n)\nw mi\nn180\nFl\no\nm\nL/12\n6\n0\n(\nH\nm 120S\no V\nott K ) 60 ( h\n,\nb\ndl\ne\nm\np. (\n5\n5\n6\n8\n0\n0\n0\n)\n-1\nmi d -t e 540 C\n,\ne\nrB e\nd\nfive shutdown events\n1002\nU p p 1st 2nd 3rd 4th 5th 99 C o n\n98\n.\n(\n0 200 400 600 800 1000 1200 %\n)\nTime on stream (h)\nSupplementary Figure S43. Industrial side-line long-term test of\nRu -CuRu -AuRu /NPC. Total metal loading: 0.1 wt.%. Reaction conditions: Gaseous macro meso micro\nflow = 60 - 200 mL/min, V = 100 mL, 520 – 540 K.\nCat\nActions in the manuscript:\nPage 21, Lines 391-398: As an attempt for the practical applications, an industrial\nside-line test using an ultra-low-loading Ru -CuRu -AuRu /NPC (total metal\nmacro meso micro\nloading 0.1 wt.%) sustained ~99.3% acetylene conversion and >99.5% VCM\nselectivity over ~1200 h (Figure S43). Ultra-low coke (2.36 wt.%, Figure S44) was\ngenerated, demonstrating that the built-in tandem architecture is durable and scalable\nunder realistic operating conditions. Together with the techno-economic evaluation in\nTable S11, which shows a >16% reduction in catalyst-related cost per ton of VCM\ncompared with the HgCl /AC benchmark. These results underscore the practical 2\nfeasibility of the hierarchical tandem system.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n3. - Insufficient Verification of Reproducibility and Universality in Catalyst\nPreparation: Although the paper mentions the feasibility of the \"selective pore-filling\nstrategy\" on Al₂O₃ supports, it does not provide catalytic performance data of the\ncatalyst on this support, making it impossible to prove the universality of the strategy\nfor different supports. Additionally, the specific calculation method for \"volume\nmatching between solvent and pores\" (e.g., how to accurately measure micropore\nvolume to determine the dosage of IL4) and the recovery and recycling schemes for\nionic liquids (IL3, IL4) are not mentioned. If IL3/IL4 cannot be recycled, the\npreparation cost will increase, limiting large-scale application.\nResponse: We thank the reviewer for these constructive comments. In the revised\nmanuscript and Supplementary Information we have clarified (i) the scope of\nuniversality of the pore-filling strategy, (ii) the calculation method used for volume\nmatching between solvent and pores, and (iii) the treatment and cost contribution of\nIL3 and IL4.\n(i) Universality of the preparation strategy on Al O support\n2 3\nOur intention in using hierarchical Al O was to demonstrate that the pore-selective\n2 3\nfilling method itself is transferable to non-carbon supports at the structural level. As\nshown in Supplementary Figures S39-S41, the same capillarity- and\nimmiscibility-driven protocol yields a similar stepwise filling behaviour on\nhierarchical Al O , confirming that the engineering concept of selective pore filling is\n2 3\nnot restricted to NPC.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nWe fully agree that a rigorous evaluation of catalytic performance on Al O would\n2 3\nbe valuable. However, under strongly chlorinating EDC + C H feeds, oxide supports\n2 2\nsuch as Al O are prone to surface chlorination and phase changes, and their\n2 3\nperformance is limited in VCM manufacture. We have evaluated the performance, as\nshown in Figure S43. High performance is difficult to achieve when the support is\nchanged to Al O , mainly due to the irreplaceable role of carbon material in the\n2 3\nacetylene activation process. Actually, only carbon material was reported to be used\nas support for the VCM production without any reports using other material (oxide,\ncarbide, etc.) as the catalyst support. (Nature Communications 2021, 12, 4016).\nAccording to above discussion, necessary modifications have been made in the\nmanuscript.\nPages 20-21, Lines 384-391: The pore-selective filling strategy, relying on capillary\ninfiltration and solvent immiscibility, is also experimentally validated on non-carbon\nporous matrices (e.g., hierarchical porous Al O , Figures S39-S41). However, when\n2 3\nthe support is changed to Al O , an unsatisfied catalytic performance is presented\n2 3\n(Figure S42), mainly due to its irreplaceable function of carbon material as support for\nactivating acetylene.51 Furthermore, the lack of nitrogen-based metal coordination in\nAl O fundamentally determines the different catalytic behavior. Thus, the\n2 3\nnon-carbon material confined tandem catalysts may be more suitable in other\nreactions, which will be explored in future work.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nSupplementary Figure S42. Reaction rates of Ru -CuRu -AuRu /Al O and\nmacro meso micro 2 3\nRu -CuRu -AuRu /NPC. Reaction conditions: GHSV = 10,000 h-1, 573 K, 20 vol.%\nmacro meso micro Total\nC H , 20 vol.% EDC, 60 vol.% VCM.\n2 2\n(ii) Calculation of “volume-matched” IL dosage\nIn response to the reviewer’s request, we have now explicitly described how the IL\ndosage is determined. Necessary modifications have been added to Supplementary\nExperimental 1.1 (Catalyst preparation) and the discussion around Figure 2c and\nSupplementary Figure S7 has been expanded. Pages 5-6 in 1.2.1 Catalyst\ncharacterization: The mesopore volume was estimated as the difference between the\nmicropore volume and the mesopore volume determined from mercury porosimetry\nmeasurements. Macropore volume was obtained from mercury porosimetry.\nThe volume of IL used in the first microporous impregnation step is set to 20 % of\nthe total pore volume (corresponding to the micro pore volume) to ensure the\nsaturation of micropores without the filling in meso- and macro- pores (Figure S5-S7).\nThe mesopore contribution becomes negligible at an IL loading of ~50 vol.%, while\nfurther IL addition mainly affects the macropore region.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nActions in the Supporting Information:\nPages 3-4 (Excerpt): Using Ru -CuRu -AuRu /NPC as an example, the\nmacro meso micro\nselected metal precursors for the AuRu component (RuCl ·xH₂O, 99.9%;\n4\nin1-butyl-3-methylimidazolium chloride ([BMIM+-Cl-], IL4, LICP) with a lower\ndecomposition temperature (T = 557 K) and then stirred for 1 h. The obtained\nd\nsolution was added dropwise to the NPC material under magnetic stirring. The\nnominal metal loading of Ru and Au was controlled at 0.5 wt.% and 1 wt.%,\nrespectively. The amount of IL4 used was set to match the determined microporous\npore capacity of the NPC material. As shown in Supplementary Figures S5–S7, the\nmicropore contribution is essentially blocked when the IL loading reaches 20 vol.%\n(corresponding to the micropore volume). Therefore, in the first impregnation step,\nthe IL4 volume was fixed at 20 vol.%, ensuring that the micropores were effectively\nsaturated without forming a bulk liquid phase outside the pores. Subsequently, the\nsample was decomposed at 587 K (heating rate 5 K min-1, hold time 1 h, static N\n2\natmosphere) to fully decompose IL4, allowing the metal components to remain in the\nmicropores.\nWe emphasize in the text that these values represent the centres of practical\noperating windows. Small deviations in pore volume or IL dosage do not change the\noverall filling sequence (micropores → mesopores → macropores), as corroborated\nby the combined N sorption, mercury intrusion, and FIB–SEM/EDS analyses\n2\n(Figures 2c, d and Supplementary Figures S7, S40–S42).\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n(iii) Recycling and cost contribution of IL3 and IL4\nWe agree that the fate of IL3 and IL4 is important for assessing scalability. In our\nsynthesis: IL4 ([BMIM+-Cl-]) serves as the metal-precursor solvent and is fully\ndecomposed during calcination (587–776 K); IL3 ([BMIM+-Tf N-]) is used as a\n2\nsacrificial blocking agent and is likewise decomposed during the final\nhigh-temperature calcination step. Therefore, in the present work IL3 and IL4 are not\nrecycled and must be treated as consumables.\nTo address the reviewer’s concern about cost, we have updated the\ntechno-economic analysis in Supplementary Table S11. In the revised version, the\n“metal cost” of ~ 80 USD·kg⁻¹-catalyst explicitly includes both the noble metals and\nthe sacrificial IL3/IL4, estimated from typical commercial prices and the\nexperimentally used IL dosages. Even under the conservative assumption that all ILs\nare non-recyclable, their contribution remains <10% of the total catalyst cost. After\nnormalization to VCM productivity and considering the process advantage of the\ntandem EDC + C H route, the Ru -CuRu -AuRu /NPC catalyst still reduces\n2 2 macro meso micro\nthe cost per ton of VCM by approximately >16% compared with the industrial\nHgCl₂/AC catalyst, while completely eliminating mercury emissions.\nSupplementary Table S11. Techno-economic comparison of HgCl /AC vs.\nmacro meso micro\nItem HgCl /AC Ru -CuRu -AuRu /NPC\n2 macro meso micro\nMetal loading a\n10 0.1\n(wt.%)\nCatalyst cost b\n≥ 15 ~ 80\n(USD/kg-catalyst)\nCatalyst operational VCM\nproductivity c 1 × (baseline) > 2 ×\n(normalized)\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nCatalyst cost normalized to\nVCM output d ≥ 15 ≤ 40\n(USD/t-VCM)\nEnvironmental hazard /\ndisposal cost e 15–20 ~ 0\n(USD/kg)\nProcess advantage of EDC +\nC₂H₂ tandem pathway f 0 –10 (savings)\n(USD/t-VCM)\n~ 0\nPrecious-metal recovery credit\n(treated as\ng –15 to –20\nhazardous\n(USD/kg-catalyst)\nwaste)\nCatalyst cost after metal\nrecovery h ≥ 30–35 60 – 65\n(USD/kg)\nFinal total cost per ton VCM i\n≥ 30–35 ~ 25–28\n(USD/t)\na Metal loading. HgCl /AC typically contains ≥10 wt.% Hg (elemental basis).\nmacro meso micro\nb Catalyst cost. Computed based on the average market price over the past five years (Hg ≈ 0.03\nUSD/g, Au ≈ 62 USD/g, Ru ≈ 15 USD/g, Cu ≈ 0.0083 USD/g, IL3-4 ≈ 10–30 USD·kg⁻¹).\nc Productivity normalization. The EDC + C₂H₂ cascade produces 2 mol VCM per cycle, vs. 1 mol\nVCM in the Hg-based single-step acetylene hydrochlorination.\nd Cost per ton VCM. Catalyst cost normalized by VCM productivity. High activity and >2×\ncapacity means Ru -CuRu -AuRu /NPC requires much less catalyst per unit VCM.\nmacro meso micro\ne Environmental disposal cost. Hg catalysts demand hazardous waste treatment (≥15–20 USD/kg).\nNPC-based catalyst contains no toxic metals, negligible disposal cost.\nf Process advantage of tandem reaction. EAC eliminates additional separation steps and the second\nreactor, at least 10 USD/t-VCM savings (conservative).\ng Recovery credit. Au and Ru prices are taken from current market data. ≥90 % recovery of Au/Ru\nby [AlCl₄]⁻-based ionic-liquid leaching (Ref. ACS Omega 2023,8, 8341−8345) is assumed, and\nthe corresponding metal-recovery credit is included in the net catalyst cost.\nh Net catalyst cost. Hg remains ≥30–35 after disposal; Ru–CuRu–AuRu falls to approx. 60–65\nUSD/kg after metal recovery.\ni Final cost per ton VCM. After combining catalyst cost normalization, process advantage and\nmetal recovery: HgCl /AC ≥ 30–35 USD/t, Ru -CuRu -AuRu /NPC ~ 25–28 USD/t.\n2 macro meso micro\n4. Lack of Direct Characterization for the Spatial Distribution of Active Components\nin Hierarchical Pores: Existing characterization methods (e.g., HAADF-STEM) can\nonly observe the structure of active components in single-pore catalysts (e.g.,\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nmacropore-only Ruₘₐ ᵣₒ/NPC), but cannot directly prove the spatial distribution of\nc\n\"three active components located in macropores, mesopores, and micropores\nrespectively within the same catalyst\" (due to the disordered structure of hierarchical\npores, it is difficult to achieve atomic-resolution overall imaging). Although indirect\ninference is made through XAS coordination environment analysis and single-pore\nreference samples, direct evidence (e.g., three-dimensional distribution\ncharacterization by focused ion beam scanning electron microscopy (FIB-SEM)\ncombined with elemental mapping) is lacking, which may lead to disputes over the\nstructural confirmation of \"pore-selective confinement\".\nResponse: We thank the reviewer for this constructive suggestion. In the revised\nmanuscript, we now provide direct cross-sectional visualization of the hierarchical\npore filling by FIB-SEM combined with element-specific line-scan analysis, as shown\nin the new Figure 2d.\nA cross section with a length of ca. 19.75 μm and a milling depth of 6.11 μm was\nprepared on a representative Ru -CuRu -AuRu /NPC catalyst (Figure 2-d1).\nmacro meso micro\nAlong this cross section, three characteristic pores can be seen: macropores,\nmesopores, and micropores. Elemental line scans across these regions (Figure 2-d2)\nclearly reveal pore-specific metal distributions. In the macropore region, a\npronounced Ru signal is observed, whereas Cu and Au signals are essentially at\nbackground level, indicating that Ru species predominantly reside in macropores. In\nthe mesopore region, both Cu and Ru signals are detected with comparable intensity,\nconsistent with the presence of CuRu sites confined in mesopores. In contrast, the\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nmicropore-rich region displays strong Au and Ru signals but negligible Cu,\ndemonstrating that AuRu sites are preferentially located in micropores.\nThese FIB-SEM/EDS results provide direct spatial evidence that Ru, CuRu and\nAuRu components are selectively confined in macro-, meso- and micropores,\nrespectively, in excellent agreement with the stepwise pore-volume evolution, XAS\ncoordination analysis and reference single-pore catalysts discussed in Figure 2a–c and\nFigures. S5–S15. We have revised the text around Figure 2d to highlight this new\npiece of evidence and to better articulate how it supports the capillarity-driven\npore-selective filling strategy.\nThe supplemented data has been added and analyzed in Page 11, Lines 185-196,\nwith the revisions been highlighted.\nFigure 2. Characterizations of hierarchical pores confined catalysts. (d1) FIB-SEM images and (d2)\nEDS profiles across the marked regions of Ru -CuRu -AuRu /NPC.\nmacro meso micro\n5. Lack of Comprehensive Comparison with Existing Industrial Catalysts: The paper\nonly compares the prepared catalyst with \"physical mixing systems\" and\n\"single-active-component systems\", but not with high-performance mercury-free\ncatalysts that have been industrially applied or reported in recent years in terms of\nkey indicators (e.g., space velocity tolerance, temperature window, HCl utilization\nrate, by-product selectivity). For example, in industrial EAC reactions, trace\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nimpurities in raw materials (e.g., H₂S, CO) may affect the reaction, but the paper\ndoes not investigate the inhibitory effect of impurities on catalyst activity, making it\nimpossible to confirm its applicability in actual industrial raw materials. Moreover,\nthe catalytic performance evaluation in the paper is mainly conducted under fixed\nexperimental conditions (e.g., temperature of 573 K, EDC/C₂H₂ molar ratio of 1:1),\nand the influence of reaction parameter fluctuations (e.g., temperature variation, raw\nmaterial ratio change) on catalytic performance is not investigated. For instance,\nlocal temperature fluctuations may occur in industrial reactors due to the different\nthermal effects of EDC dehydrochlorination (endothermic) and acetylene\nhydrochlorination (exothermic), but the paper does not study the catalyst stability\nunder temperature gradients. Additionally, the influence of catalyst shaping processes\n(e.g., industrial production requires forming into particles or honeycombs) on pore\nstructure and mass transfer efficiency is not mentioned, making it difficult to directly\nconnect with industrial applications.\nResponse: We appreciate the reviewer’s insightful comments on industrial relevance.\nIn the revised manuscript we have strengthened the comparison with industrial\nbenchmarks and explicitly evaluated the catalyst under realistic process conditions,\nincluding trace impurities, parameter fluctuations and temperature gradients.\n(i) Industrial side-line test under ultra-low metal loading.\nTo directly address industrial applicability, an ultra-low loading\nRu -CuRu -AuRu /NPC catalyst was prepared and tested in an industrial\nmacro meso micro\nside-line unit. The catalyst was loaded into a fixed bed connected in parallel with a\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\ncommercial reactor and operated for >1100 h on stream (five start-up/shutdown\nevents) using unpurified EDC and acetylene feeds. The total metal loading is 0.1 wt.%,\nwhich lies within the loading range of industrial Ru/Au catalysts. The gas hourly\nspace velocity fluctuated between 60-120 h⁻¹ (due to routine flow adjustments), and\nthe bed temperatures at the upper, middle and bottom sections varied within ca.\n540–580 K, thus inherently introducing realistic temperature gradients and operational\nperturbations. As shown in Supplementary Figure S43, the acetylene conversion\nremained at ~99.3 % throughout the test and the vinyl chloride selectivity\nwas >99.5 %, evidencing that the built-in tandem catalyst sustains near-equilibrium\nperformance under industrially relevant conditions and space-velocity variations.\n)\nw mi\nn180\nFl\no\nm\nL/12\n6\n0\n(\nH\nm 120S\no V\nott K ) 60 ( h\n,\nb\ndl\ne\nm\np. (\n5\n5\n6\n8\n0\n0\n0\n)\n-1\nmi d -t e 540 C\n,\ne\nrB e\nd\nfive shutdown events\n1002\nU p p 1st 2nd 3rd 4th 5th 99 C o n\n98\n.\n(\n0 200 400 600 800 1000 1200 %\n)\nTime on stream (h)\nSupplementary Figure S43. Industrial side-line long-term test of\nRu -CuRu -AuRu /NPC. Total metal loading: 0.1 wt.%. Reaction conditions: Gaseous macro meso micro\nflow = 60 - 200 mL/min, V = 100 mL, 520 – 540 K.\nCat\n(ii) Tolerance to trace impurities and by-product formation.\nIn the side-line test, the industrial EDC and acetylene feeds contained typical trace\nimpurities, including H (~75 ppm), O (~10 ppm), H O (~100 ppm) and CO/CO\n2 2 2 2\n(~20 ppm). No H S has been detected in current VCM-synthesis process. These levels\nNature Communications\nare below the reported poisoning thresholds of Ru, CuRu and AuRu sites, and,\nconsistent with the stable performance during the 1200 h test (Supplementary Figure\nS43). Gas chromatography analysis of the outlet stream detected no additional\nchlorinated by-products above the detection limit (~100 ppm), in line with industrial\nexperience that both the EAC route and conventional acetylene hydrochlorination\ntypically deliver VCM selectivities above 99% with negligible formation of other\nchlorinated hydrocarbons (React. Chem. Eng., 2018, 3, 34-40, Chinese Journal of\nCatalysis, 2022, 43, 820-831. Catal. Sci. Technol., 2016, 6, 1402-1409, Ind. Eng.\nChem. Res., 2019, 58, 5404-5413).\n(iii) Comparison with state-of-the-art mercury-free catalysts.\nWe agree with that a clearer benchmark against mercury-free systems is helpful. It\nshould be noted that most high-performance Hg-free catalysts reported to date are\ndesigned for single-step acetylene hydrochlorination, whereas our system targets the\ntwo-step EDC + C H cascade (EAC), for which industrial catalyst standards are still\n2 2\nemerging. To provide a quantitative context, we have now added a summary table\n(new Supplementary Table S11) comparing our Ru -CuRu -AuRu /NPC\nmacro meso micro\ncatalyst with representative state-of-the-art Hg catalysts for VCM manufacture\n(detailed disscussed were shown in your previous reponse). Thee results demonstrate\nthat, despite employing noble metals, the hierarchical catalyst delivers a >16%\nreduction in cost per ton of VCM while completely eliminating mercury emissions.\nThis analysis highlights the practical industrial relevance of built-in tandem catalysis\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nand underscores its potential as a sustainable replacement for Hg-based acetylene\nhydrochlorination technologies.\n(iv) Effect of temperature gradients and operating parameter fluctuations.\nWe agree with that local temperature non-uniformity is inevitable in industrial\nreactors because EDC dehydrochlorination is endothermic while acetylene\nhydrochlorination is exothermic. The industrial side-line experiment inherently\nincludes such gradients: the three thermocouples positioned at the upper, middle and\nbottom sections of the bed show persistent but moderate temperature differences\nduring operation (Supplementary Figure S43). Nevertheless, the acetylene conversion\nand VCM selectivity remain essentially constant, indicating that the hierarchical\narchitecture mitigates hot-spot formation and internal diffusion limitations. In addition,\nthe results show that the catalyst maintains >99.3 % acetylene conversion and >99.5 %\nVCM selectivity across these ranges, confirming robustness against typical process\nfluctuations. Corresponding discussion has been added in Page 21, Lines 391-398:\nAs an attempt for the practical applications, an industrial side-line test using an\nultra-low-loading Ru -CuRu -AuRu /NPC (total metal loading 0.1 wt.%)\nmacro meso micro\nsustained ~99.3% acetylene conversion and >99.5% VCM selectivity over ~1200 h\n(Figure S43). Ultra-low coke (2.36 wt.%, Figure S44) was generated, demonstrating\nthat the built-in tandem architecture is durable and scalable under realistic operating\nconditions. Together with the techno-economic evaluation in Table S11, which shows\na >16% reduction in catalyst-related cost per ton of VCM compared with the\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nHgCl /AC benchmark. These results underscore the practical feasibility of the\n2\nhierarchical tandem system.\n(v) Catalyst shaping and mass-transfer considerations.\nWe fully agree with the reviewer that shaped bodies (pellets, rings or honeycombs)\nwill ultimately be required for large-scale reactor implementation. The present work,\nhowever, is primarily aimed at elucidating the intrinsic tandem mechanism and the\nstructure–performance relationships of the hierarchical catalyst. For this reason, all\ncatalytic tests reported in the manuscript, including the industrial side-line evaluation,\nwere carried out using sieved powders in the 40–60 mesh range, which is the standard\npractice in gas-phase acetylene hydrochlorination kinetics to minimize external and\ninternal diffusion limitations. We have now clarified the particle size in the\nSupplementary Experimental 1.1 Catalyst preparation.\nAccording to your suggestion, we have syudied the internal and external mass\ntransfer limitations.\nActions in Supporting Information\nPages 21-22:\n2.3 Internal and external mass transfer limitations\n2.3.1 Internal Diffusion: Weisz-Prater Criterion\nThe absence of internal mass transfer limitations was evaluated using the\nWeisz-Prater criterion, where if C is lower than 1, the internal mass transfer effects\nWP\ncan be neglected:\n-r' ρ R2\nC = A(obs) c <1\nWP\nDeCAS\n-r' = Observed reaction rate: 4∙10-8 kmol∙s-1kg-1\nA(obs) Cat\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nρ = Solid catalyst density: 400 kg m-3\nc\nR = Particle radius: 4∙10-5 m\nC = Concentration of reaction gas at the surface of the catalyst.\nAS\nC = 2.14∙10-2 kmol∙m-3\nAS\nD = Effective gas-phase diffusity:\ne\nD =\nDABεpσc\ne\nτ\nD = Gas-phase diffusivity.\nAB\nD for a mixture was calculated according to Perry’s Chemical Engineer’s Handbook\nAB\nto be 12.56·10-5 m2/s\nε = Pellet porosity = 0.5,\np\nσ = Constriction factor = 0.6,\nc\nτ = Tortuosity = 3,\nD = 1.256∙10-5 m2∙s-1\ne\nSolving equation (S. 1)\n4∙10-8 kmol s-1∙kg -1 ∙400 kg m-3 (4∙10-5 m) 2\nC = Cat Cat =9.52∙10-8≪ 1\nWP 1.256∙10-5 m2s-1∙2.14∙10-2 kmol m-3\nTherefore, the result proves that our catalyst does not suffer from internal mass\ntransfer limitations.\n2.3.2 External Diffusion: Mears Criterion\nThe absence of external mass transfer limitations can be evaluated using the Mears\ncriterion:\n-r' ρ Rn\nA c <0.15\nkcCAS\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\n-r' = Observed reaction rate: 4∙10-8 kmol∙s-1kg-1\nA(obs) Cat\nρ = bulk density of the catalyst bed: 400 kg∙m-3\nc\nR = Particle radius: 4∙10-5 m\nn = reaction order If n = 2 (Real reaction order n < 2)\nC = Concentration of reaction gas at the surface of the catalyst.\nAS\nC = 2.14∙10-2 kmol∙m-3\nAS\nk = mass transfer coefficient (m s-1) = 0.14 m s-1\nc\nk can be calculated from the Sherwood number.\nc\nSh=\nkcdp=0.91∙0.91∙Re0.49∙Sc1/3\nDA\nSolving equation (S.3):\n4∙10-8kmol s-1∙kg -1 ∙400kg m-3∙4∙10-5m∙2\nCat Cat =4.27∙10-7 ≪ 0.15\n0.14m∙s-1∙2.14∙10-2kmol m-3\nTherefore, the external mass transfer limitations could also be excluded.\nIn addition, several observations indicate that mass-transfer limitations are not\ndominant under our conditions. First, the hierarchical NPC support exhibits a high\ntotal pore volume (1.47 cm3·g-1, Table S5) and macro-meso-micropores confined\nmetal sites provide short diffusion paths for gaseous reactants. Second, the acetylene\nconversion profiles as a function of bed length (Figure 3c) increase smoothly without\nthe sharp fronts or plateaus that are typically associated with strong internal diffusion\nor external film-diffusion control. Third, in the industrial side-line test\n(Supplementary Figure S43) the temperatures recorded at the upper, middle and\nbottom bed positions remain within a relatively narrow window (540–580 K) and no\npronounced hot spot is observed, while the outlet acetylene conversion stays at 99.3 %\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nthroughout >1200 h on stream. Such behaviour is consistent with reaction-controlled\nkinetics rather than diffusion-limited operation.\nA systematic engineering study of catalyst shaping and reactor design (e.g., pellet\nor monolith formulation, mechanical strength, pressure drop, and preservation of the\nhierarchical porosity during forming) is indeed essential for future industrial\ndeployment. We believe that the present data, obtained on small-particles under\nconditions where mass-transfer artefacts are minimized, are sufficient to support the\nmechanistic concept of built-in tandem catalysis in hierarchical pores.\n6. Although the paper emphasizes that the catalyst has a \"total metal loading of only\n0.28 wt.%\" and a stability of 700 hours, its industrial application still faces economic\nbottlenecks:\n- Procurement and Recovery Costs of Precious Metals: The catalyst contains two\nprecious metals (Au and Ru). Although the loading is low, large-scale industrial\nproduction requires a huge amount of catalysts (e.g., a 10,000-ton VCM plant\nrequires dozens of tons of catalysts), resulting in high procurement costs for precious\nmetals. Meanwhile, the paper does not mention the recovery process of precious\nmetals from spent catalysts. If precious metals cannot be recovered, it will not only\ncause resource waste but also increase the cost of solid waste treatment, weakening\nthe market competitiveness of the technology.\nResponse: We appreciate the reviewer’s concern regarding the economic implications\nof using Au- and Ru-containing catalysts at industrial scale and the recovery of the\nspent catalysts.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nFirst, the hierarchical Ru -CuRu -AuRu /NPC catalyst operates with a low\nmacro meso micro\ntotal noble-metal loading (0.1 wt.% in the industrial side-line formulation) while\ndelivering >2× higher VCM productivity per reactor pass than the benchmark\nHgCl /AC system. After normalizing to VCM output, the required noble-metal\n2\ninventory per ton of VCM is comparable to or lower than that of current Ru/Au\ncatalysts, whereas the overall catalyst cost per ton of VCM is reduced from ≥30–35\nUSD t⁻¹ for HgCl /AC to ~25–28 USD t⁻¹ for Ru -CuRu -AuRu /NPC. In\n2 macro meso micro\nthis analysis we conservatively treat the ionic liquids (IL3/IL4) used during synthesis\nas sacrificial (non-recycled) reagents and fully charge their one-time consumption into\nthe catalyst price.\nSecond, with respect to noble-metal recovery, we have previously developed an\n[AlCl ]⁻-based ionic-liquid leaching system that dissolves Au, Pd and Pt efficiently\n4\nunder mild conditions and was successfully applied to reactivate Au0 formed in\ndeactivated VCM catalysts, thereby enabling closed-loop recycling of the noble\nmetals (ACS Omega 2023, 8, 8341-8345).\nIn the revised manuscript we now explicitly state that Au and Ru in the hierarchical\ncatalyst can be recovered by the same IL-based oxidative leaching concept, followed\nby conventional hydrometallurgical processing. Based on the dissolution efficiencies\ndemonstrated in this prior work, a conservative ≥90 % Au/Ru recovery is assumed in\nthe techno-economic model, which yields a metal-recovery credit of 15–20 USD per\nkg of spent catalyst (see updated footnote g in Supplementary Table S11). Even under\nthese conservative assumptions, the overall cost of VCM production remains ~25–28\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nUSD t⁻¹, while completely eliminating mercury usage, which substantially mitigates\nthe economic bottleneck highlighted by the reviewer. Meanwhile, there have been\ntremendous industrial practices for the noble metal recovery by various methods. We\ntherefore think that the recycle of the spent catalys may not be the main concern for\nthe industrial applications.\n7. The paper only verifies the catalyst stability within 700 hours (acetylene conversion\nrate maintained at ~99.3%), but industrial catalysts need to operate continuously for\nthousands of hours and must cope with issues such as coking, active component loss,\nand bed pressure drop change. The paper points out that hierarchical pores can\nreduce coking, but it does not quantitatively analyze the coke content of the catalyst\nafter 700 hours (e.g., measuring coke rate via thermogravimetric analysis (TGA)). In\nindustrial production, reactants (especially acetylene) may undergo polymerization\nreactions to form coke when in long-term contact with active sites. If coke adheres to\nmicropore AuRu sites or blocks mesopore channels, it will lead to a decrease in\nacetylene adsorption capacity and hindered intermediate transfer, eventually causing\ncatalyst deactivation.\nResponse: We fully agree that long-term stabilityare critical for industrial\nimplementation. In the revised manuscript we have evaluated the side-line test of the\nhierarchical Ru -CuRu -AuRu /NPC catalyst in the industrial plant under\nmacro meso micro\nindustrially relevant conditions (Supplementary Figure S43). Throughout this 1200 h\nrun, the acetylene conversion remained at >99.3 % and the vinyl chloride selectivity\nexceeded 99.5 %, without any noticeable increase in reactor pressure drop. This result\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nsufficiently proves the excellent stability of the Ru -CuRu -AuRu /NPC,\nmacro meso micro\nwhich may show great potential for the industrial appllications.\nAs to the concern about the coked carbon on the catalyst, we performed\nthermogravimetric analysis (TGA) of the fresh and the catalyst after 1200 h stability\ntest. As shown in the newly added Supplementary Figure S44, the weight-loss profiles\nof the fresh and used samples almost overlap. Only ~2.36 wt.% carbonaceous deposits\nwere detected after 1200 h on stream test. This low coke content suggests that the\nreactant (acetylene) could be promptly converted and the product was rapidly\ndesorbed at the moderate reaction temperature and high space velocity, which avoids\nthe possible poymeriztion. This result is in line with the robust catalytic performance,\nproving its superior stability. We have added these data and discussions in the revised\nSupplementary Information and in the stability section of the main text.\n80\n%)\nht\n( 60\ng\nei\nW 40\nUsed\n0\n360 540 720 900\nTemperature (K)\nSupplementary Figure S44. TGA curves of the fresh and used (1200 h)\nRu -CuRu -AuRu /NPC catalysts.\nmacro meso micro\n8. III. Conclusion\nThe paper is not recommended for publishing in nature communication.\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China\nNature Communications\nResponse: We sincerely thank the reviewer for the very careful and critical evaluation\nof our work. In the revised manuscript we have substantially expanded both the\nexperimental and theoretical evidence to address the concerns raised in Comments\n1–7. With these revisions, we believe that the major issues regarding mechanism\nvalidation, reproducibility, and industrial/economic feasibility have been\nsubstantively resolved, while the core conceptual advance, built-in tandem catalysis\ninside a single hierarchical porous catalyst with spatially ordered Ru/CuRu/AuRu\nsites and near-thermodynamic VCM production, remains unique and is now much\nmore convincingly demonstrated. We hope you will reconsider the revised\nmanuscript for the publication.\nSincerely,\nDing Ma\nCollege of Chemistry, Beijing University, Beijing, China\ndma@pku.edu.cn\nNO. 18 Chaowang Road, Zhejiang University of Technology, Hangzhou, 310014, China"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The revised manuscript is improved accordingly to my suggestions and comments I recommend for publication.", "reviewer_2": "The authors have revised their manuscript according to the reviewer's comments, and it can be accepted for publication."}, "author_response": ""}]

Decision letter