Efficient and stable catalytic hydrolysis of perfluorocarbon enabled by SO_2-mediated proton supply

Domain: physics
Published: 2026-01-14
Editorial outcome: minor_revision

Abstract
Catalytic hydrolysis is an effective strategy for decomposing tetrafluoromethane (CF4), one of the most chemically inert per- and polyfluoroalkyl substances (PFAS). A key challenge in this process lies in enhancing proton availability to facilitate efficient and stable C–F bond activation while ensuring long-term catalyst stability. Here we present an SO2-driven approach to significantly enhance H2O dissociation and proton-supplying through the in situ formation of Al–HSO4 and Ga–HS species. Combined experimental and theoretical investigations reveal that these species not only lower the energy barrier for C–F bond activation but also promote active site regeneration by facilitating defluorination, thus effectively overcoming catalyst deactivation. As a result, the optimized catalyst enables complete CF4 decomposition at a low temperature of 550 °C, with stable operation for over 2500 hours. This work establishes a new paradigm for regulating proton transfer and offers a viable route for the efficient, durable degradation of gaseous PFAS.

Introduction
Gas phase per- and polyfluoroalkyl substances (PFAS) are among the most persistent environmental pollutants, owing to their exceptional chemical inertness, high ecological risk, and substantial climate impact1,2. Among them, tetrafluoromethane (CF4) is particularly concerning due to its extremely high global warming potential (GWP), ~7390 times higher than that of CO2, coupled with an exceptionally long atmospheric lifetime exceeding 50,000 years3,4. Major CF4 emissions arise from industrial activities such as aluminum electrolysis and semiconductor manufacturing, where it is an unavoidable byproduct5–8. In response to the environmental risks posed by CF4, the European Union implemented the Carbon Border Adjustment Mechanism (CBAM) in 2022, mandating stringent emission control9. Therefore, developing efficient, energy-saving, and sustainable technologies for CF4 decomposition is crucial for achieving global climate mitigation goals.

Catalytic hydrolysis has emerged as a highly promising approach for CF4 decomposition, offering notable advantages in terms of high reaction rates, industrial scalability, and compatibility with existing infrastructure3. Nevertheless, the challenge lies in breaking the exceedingly strong C–F bonds, which have an extremely high bond dissociation energy of approximately 543±4 kJ mol−1 and confer exceptional stability to CF4 4,10,11. Significant efforts have been dedicated to develop catalysts capable of activating and cleaving these robust bonds under relatively mild conditions. A growing body of evidence underscores the critical role of surface hydrogen species (i.e., protons) in this process12–14. For instance, Chen et al. demonstrated that the interaction of surface protons with C–F bonds significantly lowered the activation barrier and reaction temperature for CF4 decomposition15. Zhang et al. advanced this approach by employing Ga–OH groups as defluorination sites, achieving remarkable stability over 1000 h16. Similarly, Luo et al., utilizing constrained ab initio molecular dynamics (cAIMD), confirmed the essential role of surface hydroxyl groups in CF4 hydrolysis17. Collectively, these findings emphasize that proton availability not only facilitates C–F bond activation but also plays a key role in regenerating fluorinated active sites, thus ensuring sustained catalytic performance. Despite these advances, enhancing proton supply during hydrolysis remains a significant bottleneck. Traditional proton sources often suffer from thermal instability or rapid desorption at elevated temperatures, especially under industrial reaction conditions. This highlights the urgent need for new strategies that can enable persistent proton availability while maintaining high-temperature stability.

Sulfur dioxide (SO2), typically regarded as a catalyst poison due to its strong adsorption affinity, is frequently co-emitted with CF4 in industrial flue gases, particularly from aluminum electrolysis processes5–7. Intriguingly, under hydrolysis-relevant conditions, SO2 readily forms strongly acidic and thermally stable surface species, such as hydrogensulfite or bisulfate (–HSO3/–HSO4)18,19. These SO2-derived surface species possess high acidity, robust thermal stability, and low volatility, distinguishing them significantly from conventional proton sources which typically suffer from rapid desorption or thermal decomposition at elevated temperatures20–23. Therefore, the formation of these species on catalyst surfaces could substantially increase local proton concentrations near active catalytic sites, thus potentially overcoming existing limitations related to proton scarcity in conventional CF4 catalytic hydrolysis process.

In this work, we report a novel strategy that leverages SO2-driven in situ formation of surface proton-supplying sites to significantly enhance proton availability and thus catalytic CF4 hydrolysis. Through detailed in situ spectroscopic analyses and X-ray photoelectron spectroscopy (XPS) measurements, we identify the formation of Al–HSO4 and Ga–HS surface sites, which substantially enhance H2O dissociation and proton availability by factors of 6 and 10, respectively, compared to systems without SO2. Furthermore, comprehensive theoretical and experimental investigations reveal that these proton-supplying sites not only reduce the activation energy for C–F bond cleavage but also accelerate defluorination of active sites, thereby mitigating fluorine poisoning and enhancing catalyst durability. As a result, our optimized system achieves complete CF4 decomposition at a notably low temperature of 550 °C (comparing to the normal temperature of 700 °C) with exceptional operational stability exceeding 2500 h4. This work introduces a novel framework for in situ proton regulation and opens new possibilities for the efficient, long-term catalytic degradation of PFAS under practical industrial conditions.

Results
To evaluate the promotional effect of SO2 on CF4 catalytic hydrolysis, we selected a Ga/θ-Al2O3 catalyst with 30 mol% Ga doping, chosen for its structural stability and abundance of active sites16. Detailed procedures for catalysts synthesis and characterization are provided in the Methods section.

We first examined the influence of SO2 concentration by co-feeding CF4 with SO2 at varying levels to simulate realistic industrial exhaust conditions (Supplementary Fig. 1). The reaction temperature was maintained at 550 °C, significantly lower than that used in most previously reported CF4 decomposition system. Remarkably, the introduction of SO2 dramatically enhanced CF4 decomposition efficiency, increasing from ~60% (without SO2) to ~90% across an ultra-broad SO2 concentration range (250–20,000 ppm, Fig. 1a and Supplementary Fig. 2). This robust performance across more than three orders of magnitude demonstrates the catalyst’s wide applicability to various industrial SO2/CF4 ratios. Notably, at 5000 ppm SO2, complete CF4 decomposition was achieved at 550 °C, a record low temperature for 100% CF4 decomposition. Hence, 5000 ppm SO2 was chosen as the standard condition for subsequent evaluations.

The effect of temperature was further investigated across a range from 425 to 600 °C (Fig. 1b and Supplementary Fig. 3). In all cases, SO2 addition significantly boosted the reaction rate compared to CF4 decomposition alone, with the most pronounced enhancement observed at lower temperatures. Arrhenius analysis revealed that SO2 addition lowered the apparent activation energy for CF4 decomposition from 137.2 kJ/mol to 114.4 kJ/mol, a 17% reduction (Fig. 1c and Supplementary Figs. 4, 5). Interestingly, CF4 also promoted SO2 oxidation, reducing its apparent activation energy from 23.5 kJ/mol to just 5.3 kJ/mol, a 77% decrease. These results highlight a mutual and synergistic promotion between CF4 decomposition and SO2 oxidation pathways.

To further probe this synergistic effect, we conducted transient feed experiments involving three sequential gas feeding protocols at 550 °C (Fig. 1d). When CF4 was introduced alone, the decomposition efficiency remained below 60%. Strikingly, upon addition of SO2, CF4 decomposition rapidly increased to >99% (Fig. 1d, bottom), clearly demonstrating the promotional effect of SO2. In contrast, SO2 oxidation alone exhibited a modest conversion efficiency of ~75%; yet, co-feeding CF4 led to full conversion of both gases (>99%, Fig. 1d, top and Supplementary Figs. 6–8). Notably, this synergistic enhancement was equally evident when CF4 and SO2 were introduced concurrently from the outset (Fig. 1d, middle), confirming the strong and consistent mutual promotion effect between the two species.

To assess the long-term practical viability of this system, we conducted extended stability tests at 550 °C (Fig. 1e and Supplementary Table 1). Remarkably, the catalyst exhibited outstanding durability, maintaining nearly complete CF4 and SO2 conversion over 2500 h without any detectable deactivation, demonstrating the robustness and long-term operational viability of the system for potential industrial applications. Further, the calculated deactivation constant was 3.97×10−4 h−1, corresponding to an expected catalyst lifetime of ~2522 h, validating the long-term practical viability of this system. A comprehensive comparison with previously reported CF4 decomposition systems (Fig. 1f and Supplementary Table 2) confirms the superior performance of this system, which achieves the lowest operational temperature for full CF4 decomposition and the longest recorded lifetime under continuous flow conditions15,16,24–32. These advantages, high efficiency, excellent durability, and compatibility with SO2-containing gas streams, highlight the promise of this system for scalable and environmentally sustainable degradation of gas phase PFAS.

To elucidate the role of SO2 in enhancing proton availability during CF4 catalytic hydrolysis, we employed a suite of characterization techniques to identify the in situ formation of proton-supplying species on the Ga/θ-Al2O3 catalyst surface. X-ray diffraction (XRD) patterns of both fresh and used Ga/θ-Al2O3 catalysts (Fig. 2a) displayed only the characteristic reflections of θ-Al2O3 (JCPDS#35-0121), with no additional diffraction peaks observed16, indicating no bulk sulfur species formed during the reaction. Transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) mapping of the used Ga/θ-Al2O3 catalyst (Fig. 2b) further confirmed this observation. The used catalyst retained its nanosheet structure, and sulfur species were uniformly distributed across the surface, verifying the absence of excessive sulfur accumulation. To probe the nature of sulfur-containing species formed under reaction conditions, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was conducted (Fig. 2c). The results revealed new infrared features of –HSO4 (1000–1250 cm−1) and –HS (688 cm−1) species under anhydrous CF4 and SO2 co-feeding15,33,34. This confirmed the in situ formation of proton-supplying sites (–HSO4 and –HS) during the reaction.

To analyze the surface elemental composition, X-ray photoelectron spectroscopy (XPS) was performed on catalysts for CF4 and SO2 reactions with different SO2 concentrations (250–20,000 ppm, Fig. 2d and Supplementary Fig. 9). The results revealed clear S 2p signals characteristic of Ga–HS (~161.6 eV) and Al–HSO4 (~169.6 eV) species (Supplementary Fig. 10)35–37. The assignments were validated by comparison with standard samples and supported by thermogravimetric analysis (TG, Supplementary Fig. 11)15,38. Further comparison among catalysts with different treatments (Fig. 2e) revealed the following order in Al–HSO4 content: H2SO4-modified > SO2 treated > used catalyst, confirming the participation of –HSO4 species in the catalytic hydrolysis process. The absence of Ga–HS signals in the θ-Al2O3-used samples reinforced the conclusion that Ga–HS sites were formed exclusively in situ during the CF4 and SO2 synergistic reaction.

Figure 2f summarizes the quantifications of Ga–HS and Al–HSO4, along with the total sulfur content on the catalyst surface as a function of SO2 concentration. The ratios stabilized at ~75% (Ga–HS), ~25% (Al–HSO4), and ~3% (total S), respectively, confirming the stable in situ formation of proton-supplying sites without excessive sulfur species accumulation during the reaction.

To investigate the impact of proton-supplying sites on the catalyst’s performance, XPS and in situ DRIFTS analyses were conducted. F 1s spectra (Supplementary Fig. 12) revealed that fluorine species (AlFx), typically indicative of fluorine poisoning, were present only in CF4-alone-treated samples. In contrast, samples from CF4–SO2 reactions showed negligible AlFx signals, suggesting that proton-supplying sites effectively mitigated fluoride accumulation on active sites16. O 1s spectra revealed two major components: lattice oxygen (Olat, ~531.4 eV) and chemisorbed oxygen (Oads, ~533.0 eV)39,40. The CF4+SO2-treated sample exhibited the highest Oads content, demonstrating minimal surface oxygen damage. Additionally, the Al 2p peak at ~75.9 eV, attributed to Al–OH (a key proton donor in CF4 hydrolysis), decreased significantly under CF4 or SO2 alone but increased significantly under the synergistic reaction, confirming the restoration of proton-donating groups via SO2-derived species.

In situ DRIFTS analysis (Supplementary Fig. 13) provided further insights into the reaction dynamics. During SO2 pre-adsorption, the depletion of Al–OH groups (3650–3750 cm−1) and the formation of HSO3− species (1200 and 966 cm−1) indicated that SO2 was activated via interaction with surface hydroxyls. When CF4 was co-fed with SO2, the intensities of both adsorbed SO2 and HSO3− bands decreased due to competitive adsorption. As the reaction temperature increased above 250 °C, the transition of HSO3− to SO42− (1371 and 995 cm−1) and HSO4− (1190 cm−1) confirmed further oxidation of sulfur intermediates. Concurrently, a monotonic decline in CF4 signals and a transient rise-and-fall of HSO4− bands were observed, demonstrating the dynamic role of HSO4− in facilitating C–F bond activation during hydrolysis.

Previous studies have demonstrated that protons can effectively promote C–F bond activation through strong interactions with C–F bond, thereby facilitating hydrolysis41–44. In conventional CF4 hydrolysis, protons are primarily supplied by the dissociation of H2O. To investigate the mechanism role of SO2 in enhancing proton availability, we performed time-resolved in situ DRIFTS on Ga/θ-Al2O3 catalyst at 550 °C under various reaction conditions (Fig. 3). In the case of SO2 alone (Supplementary Fig. 14), H2O dissociation was significantly inhibited. Similarly, for CF4 decomposition alone (Fig. 3a), no significant H+ bands were detected, suggesting that limited H+ availability hindered effective C–F bond cleavage. In contrast, when SO2 and CF4 were co-fed (Fig. 3b), distinct peaks corresponding to gaseous SO2 (1379 cm−1) and CF4 (1279 cm−1) appeared initially, followed by prominent H2O dissociation and generation of surface sulfate species. Notably, vibrational features in the 2900–3400 cm−1 region (Fig. 3c), assigned to protonic species, emerged rapidly, confirming in situ H+ generation from H2O dissociation in the presence of SO2 19,20. The temporal evolution of H+ generation, H2O dissociation and sulfate species formation are shown in Fig. 3d and Supplementary Fig. 15. During the SO2 and CF4 synergistic reaction, H⁺ generation and H2O dissociation rates were ~10 and 6 times higher, respectively, than in CF4-only hydrolysis. Moreover, sulfate formation was enhanced by ~3 times compared to SO2 oxidation alone. These results demonstrated that proton-supplying sites not only accelerate H2O activation but also enhance SO2 oxidation, thereby reducing the activation barrier for CF4 hydrolysis.

To evaluate the effect of surface Al–HSO4 sites on the CF4 adsorption, DFT calculations were performed for CF4 adsorbed at different sites on the θ-Al2O3 (010) and Ga/θ-Al2O3 (010) surface (Supplementary Figs. 16, 17 and Supplementary Table 3). These results indicated that the AlIII site was the primary adsorption site for CF4, and the effect of Ga doping on this site was negligible. The intrinsic stability of Al–HSO4 sites, as well as the influence of SO2 introduction on its structural stability, was further evaluated (Supplementary Figs. 18–20). These results demonstrated that Al–HSO4 sites was intrinsically stable, and the introduction of SO2 does not compromise its structural integrity. The CF4 adsorption energy (Eads) on θ-Al2O3–HSO4 was −0.50 eV, significantly stronger than that on θ-Al2O3–OH (−0.15 eV), confirming that Al–HSO4 sites significantly enhanced the CF4 adsorption affinity (Supplementary Fig. 21 and Supplementary Table 4).

To investigate the role of Ga–HS sites in defluorination and active sites regeneration, we first studied the defluorination kinetics of AlIII active sites using constrained ab initio molecular dynamics (cAIMD) simulations (Fig. 4a, b). The energy barrier for HF elimination from fluorinated Ga sites was dramatically reduced from 2.34 eV (with Ga–OH) to 0.32 eV with Ga–HS sites, demonstrating the critical role of Ga–HS proton-supplying sites in promoting defluorination and overcoming fluorine poisoning. In addition, the effect of SO2 introduction on the stability of the Ga–HS site and the regeneration of the Ga–HS site was further analyzed by DFT calculations (Supplementary Figs. 19, 22). The results indicated that the introduction of SO2 does not disrupt the structural integrity of the Ga–HS site, and the regeneration of the Ga–HS structure is feasible (an energy barrier of 0.98 eV).

Furthermore, the regeneration behavior of active sites was investigated via in situ DRIFTS (Fig. 4c, d). In CF4-alone reactions (Fig. 4d), a rapid consumption of Al–OH was observed over time, indicating poisoning of Al active sites45. Upon H2O introduction, only partial signal recovery occurred. In contrast, under SO2 and CF4 conditions (Fig. 4c), Al–OH signals were similarly consumed, but fully regenerated after switching to H2O. Quantitative analyses of poisoning and regeneration of active sites (Fig. 4e) showed that Ga–OH sites facilitated only 49% regeneration of the active sites, while Ga–HS sites achieved complete regeneration. These results demonstrated that the in situ formed Ga–HS proton-supplying sites significantly enhanced the regeneration of fluorine-poisoned active sites.

In situ Raman spectroscopy testing was conducted to further evaluate the role of the proton-supplying sites in active site regeneration (Fig. 4f, g). For the fresh catalyst, a sharp peak at 248 cm−1 and a broad peak between 500 and 950 cm−1 were clearly observed, corresponding to the vibrations of Ga–O bonds and Al–O bonds, respectively46,47. Upon CF4 exposure, the Al–O signal diminished, indicating poisoning of Al active sites. Subsequent H2O exposure led to only partial recovery. In contrast, during the simultaneous introduction of SO2 and CF4, full regeneration of the Al–O signal was observed upon switching to H2O. Quantitative analysis of active site regeneration (Fig. 4h) revealed that complete regeneration was achieved with the assistance of Ga–HS proton-supplying sites, significantly outperforming Ga–OH (37% regeneration). These results confirmed that Ga–HS proton-supplying sites markedly enhanced the regeneration of fluorine-poisoned active sites.

The remarkable enhancement in catalytic performance is attributed to a novel promotion mechanism involving the in situ formation of proton-supplying sites, as illustrated in Fig. 5. Upon introduction, SO2 is activated by H2O on the catalyst surface to form HSO3−, which subsequently undergoes a disproportionation reaction to generate sulfur species in +6 and −2 oxidation states. The +6 sulfur species bind with Al sites to form Al–HSO4 proton-supplying sites, while the −2 species coordinate with Ga to generate Ga–HS proton-supplying sites. For the energetically challenging activation of C–F bond, the in situ formed Al–HSO4 proton-supplying sites significantly promote C–F bond cleavage by enhancing the interactions between protons and C–F bonds, thereby boosting CF4 decomposition activity. Simultaneously, the in situ formed Ga–HS proton-supplying sites effectively assist in defluorination and the regeneration of Al–F sites, leading to the complete regeneration of fluorine-poisoned Al active sites and greatly improving catalyst stability. Thus, by introducing SO2 as a promoter, the formation of proton-supplying sites is induced in situ, which greatly enhances both H2O dissociation and proton availability within the reaction system. This dual functionality results in dramatically improved activity and stability for CF4 decomposition.

Methods
Chemicals
All chemicals were obtained commercially and used as received. Aluminium isopropoxide (Al(C3H7O)3, 98.5%), Isopropyl alcohol (99.0%) and Gallium nitrate (Ga(NO3)3·xH2O, 99.9%) were purchased from Aladdin. Sulfuric acid (H2SO4) was purchased from Sinopharm.

Preparation of θ-Al2O3
θ-Al2O3 nanosheets were synthesized using a hydrothermal strategy. Specifically, 40.0 g of aluminum isopropoxide (AIP) was dissolved in 400 mL of isopropanol under continuous stirring to obtain a clear solution. Subsequently, 40.0 mL of deionized water was added dropwise to initiate the hydrolysis of AIP, followed by an additional 30 min of stirring. The resulting mixture was then divided equally into four 150 mL Teflon-lined stainless-steel autoclaves and subjected to hydrothermal treatment at 110 °C for 1 h. After naturally cooling to ambient temperature, the precipitates were dried at 80 °C for 12 h. The obtained solids were finely ground and calcined in a muffle furnace at 900 °C for 4 h with a heating rate of 1 °C min−1 to yield the final θ-Al2O3 product.

Preparation of Ga/θ-Al2O3
Ga-doped θ-Al2O3 (Ga/θ-Al2O3) catalysts were prepared via a conventional wet impregnation approach. In a typical procedure, 10.0 g of the previously synthesized θ-Al2O3 was dispersed in 400 mL of deionized water and subjected to ultrasonic agitation for 30 min to ensure uniform dispersion. An appropriate amount of gallium nitrate, corresponding to a Ga mol content of 30%, was then introduced into the suspension. The resulting mixture was ultrasonicated for an additional 30 min and subsequently concentrated using a rotary evaporator at 75 °C for 2 h. The obtained solid was dried and then calcined at 600 °C for 4 h in a tubular furnace to afford the final Ga/θ-Al2O3 catalyst.

Resource recycling
Specifically, the tail gas generated from the CF4 + SO2 reaction was first passed through 500 mL of an alkaline absorption solution containing 10 g L−1 NaOH. The concentrations of F- and SO42− ions in the resulting solution were determined by ion chromatography. To recover sulfate species, a small amount of dilute HCl solution was added to adjust the pH of the absorption solution to 7, followed by the addition of BaCl2 at a stoichiometric ratio of Ba:SO42− = 1:1 under ambient conditions. After stirring for 30 min, the resulting white precipitate was separated by centrifugation, washed three times with deionized water and three times with ethanol, and identified as BaSO4. The remaining solution was then heated in a water bath at 60 °C, and an excess amount of BaCl2 was added and stirred for 30 min. The XRD patterns confirmed that both BaSO4 and BaFCl were obtained as nearly pure phases, verifying the effectiveness of the by-product recovery process.

Characterizations
XRD patterns were recorded on a Bruker D8 Focus diffractometer with Ni-filtered Cu-Ka (λ=1.540598 Å) (40 kV, 40 mA) radiation in the 2θ range of 10–90° with a scan rate of 1°/min. TG was obtained on Perkin-Elmer Pyris 1 from ambient temperature to 1000 °C under air. XPS measurements were obtained on Thermo Fisher Scientific Escalab 250 XI, and all the binding energies were calibrated by the C 1s peak at 284.8 eV. TEM images were obtained from FEI Tecnai G2 F20 field emission transmission electron microscope operated at 200 kV.

Catalytic activity evaluation
A self-made fixed-bed reactor (Supplementary Fig. 1) was used to evaluate the CF4 and SO2 synergistic removal. The CF4 and SO2 synergistic removal reaction was conducted in a continuous flow reaction system with a quartz fixed-bed reactor (20 mm i.d.) under atmospheric pressure. The gas mixture was composed of 2500 ppm of CF4, 250–20,000 ppm of SO2 and balance in Air. The total flow rate was 33.3 mL min−1, and the gas hourly space velocity (GHSV) was about 1000 mL g−1 h−1. The SO2 and CF4 conversion rates were calculated by the following equation:

CF4 decomposition (%) = ( [CF4]in − [CF4]out ) / [CF4]in × 100%

SO2 conversion (%) = ( [SO2]in − [SO42−]out ) / [SO2]in × 100%

Where [CF4]in, [CF4]out, [SO2]in and [SO42−]out indicates the corresponding inlet and outlet gas concentrations and mass, respectively. SO42− and SO32− were detected by using a Thermo Scientific ICS-600 ion chromatograph system.

To quantitatively evaluate the catalyst stability, we calculated the deactivation constant (kd) based on the time-on-stream conversion data according to the first-order deactivation model:

ln(1 − Xf) = ln(1 − Xi) − kd * t

Xf is the final decomposition (%) of CF4. Xi is the initial decomposition (%) of CF4. t is the time throughout the reaction. τ (h): the catalyst life, τ = 1/kd.

In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)
A Thermo Fisher iS50 spectrometer was employed for recording FTIR spectra. Catalysts were pretreated by heating to 550 °C (heating rate of 20 °C min−1) and holding at 550 °C for 2 h under Air flow (30 mL min−1). Water vapor was introduced via passing through a deionized water bottle. In situ DRIFTS was used to analyze the catalytic reaction mechanism.

In situ Raman spectroscopy
The Raman was conducted on inVia Reflex (Renishaw, UK), using a 532 nm laser at a power of 50 mW. Catalysts were pretreated by heating to 550 °C (heating rate of 20 °C min−1) and holding at 550 °C for 1 h under Air flow (30 mL min−1). For the poisoning process, the catalyst was treated with reaction gas (CF4 or CF4 + SO2) for 30 min; For the regeneration process, the deactivated catalyst was treated with water vapor for 30 min.

DFT computational details
All the first-principles calculations were performed using DFT as implemented in the Vienna ab initio simulation package (VASP.5.4.4). The exchange–correlation potential is treated with the Perdew–Burke–Ernzerhof (PBE) formula using the projected augmented wave (PAW) method within the generalized gradient approximation (GGA). The cutoff energy for all calculations is set to 450 eV. All the atoms in the atomic model are optimized to the state with the smallest energy deviation. Meanwhile, a k-point Γ-centered mesh is generated for Brillouin zone samples for geometry optimization. The DFT-D3 method proposed by Grimme is applied to model the van der Waals interactions, and has been shown to accurately describe chemisorption properties. Throughout the geometry optimization process, the top two atomic layers of the supercell were permitted to relax, ensuring a realistic representation of the catalyst surface while maintaining computational efficiency. A vacuum region of 15 Å is employed to decouple the periodic replicas. In addition, the VESTA package was used to visualize the atomic structure and charge density.

The adsorption energy of –OH is defined as:

Eads = Etotal − Eslab − EOH

where Etotal is the total energy of OH adsorbed on the surface, Eslab is the energy of clean surface, EOH is the energy of the –OH.

The adsorption energy of –HSO4 is defined as:

Eads = Etotal − Eslab − EHSO4

where Etotal is the total energy of –HSO4 adsorbed on the surface, Eslab is the energy of clean surface, EHSO4 is the energy of the –HSO4.

The adsorption energies of H atom adsorption is defined as:

Eads = Etotal − Eslab − 0.5*EH2

where Etotal is the total energy of H atom adsorbed on the surface, Eslab is the energy of clean surface, EH2 is the energy of the H molecule.

cAIMD simulations
AIMD simulations are carried out via the Nose–Hoover thermostat using the canonical ensemble (NVT) at 550 °C, with a timestep of 1 fs. Constrained ab initio molecular dynamics (cAIMD) simulations with a SG sampling approach as implemented in VASP (SG-AIMD) are performed to evaluate the kinetic barriers of Al‒F bond defluorination. In this method, one suitable collective variable (CV, namely ξ) can be defined as the reaction coordinate, which is linearly changed from the initial state to the final state with a transformation velocity ξ̇. The work required to perform the transformation from initial to final states can be computed as:

W = ∫ ξ(initial) ξ(final) (∂F/∂ξ) dξ dt

where F is the computed free energy, which is evolving along with t, can be computed along cAIMD using the blue-moon ensemble with the SHAKE algorithm. At the limit of infinitesimally small ∂ξ, the needed work (Winitial-to-final) corresponds to the free-energy difference between the final and initial states. In the SG sampling, a value ∂ξ of 0.001 Å is used for each cAIMD step after testing the shorter step size for the “slow-growth”.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This work evaluated a strategy for improving CF4 decomposition performance by introducing SO2 into a Ga/θ-Al2O3 catalyst. Authors reported that SO2 addition increased the CF4 decomposition rate by approximately 90%, reduced the reaction activation energy, and enabled complete decomposition and long-term stable operation at a relatively low temperature of 550 °C. However, the following points require further discussion.\nComment\n1. The title uses the plural form \"perfluorocarbons,\" but the experiment focused on CF4 alone. It would be appropriate to add screening results for C2F6, CHF3, and SF6 as supplementary material, or to specify the title more specifically.\n2. While the CF₄ adsorption energy at a single Al³⁺ site is significant, the differences in adsorption characteristics across various surface sites on θ-Al2O3 are not considered. Additional sites should be considered for comparison of the CF4 adsorption energy results.\n3. While the CF4 adsorption energy on the Al–HSO4 surface has been presented, data on the CF4 adsorption energy on the core catalyst, Ga/θ-Al2O3 surface, is not available. A corresponding calculation is required for direct comparison.\n4. The formation energies of functional groups on the θ-Al2O3–HSO4 and θ-Al2O3–OH surfaces are not provided, making it difficult to assess the stability and potential for formation of the proposed surface structures.\n5. There is no computational basis for verifying the true stability of the Al–HSO4 and Ga–HS structures upon SO2 introduction. Energy analysis and structural optimization results are required to verify this.\n6. The mechanism of the Ga–HS structure donating protons and undergoing regeneration after the reaction, as claimed in the experiment, is not supported computationally. Analysis of the reaction pathway and energy barrier for this process is required.\nMinorly, In the main text, “Complete CF4 and SO2 conversion over 2,500 hours.” However, according to Supplementary Table S1, the SO2 conversion is approximately 95–98%. Authors should be aware of typographical errors such as molar, fourier, etc.", "reviewer_2": "This study reports an innovative approach to achieve efficient and stable CF4 hydrolysis at low temperature through SO2-driven in situ formation of proton-supplying sites. The work presents interesting results regarding C-F bond activation, resistance to fluorine poisoning and reaction mechanism. Given the significance of developing practical strategies for PFAS degradation under industrially relevant conditions, I find this study potentially impactful and recommend it for consideration in Nature Communications. However, several aspects require further clarification and improvement.\n1. The deactivation constant (kd) and expected durability are important metrics for evaluating the industrial applicability of the catalyst. While the authors report a strategy that enables 2,500 hours of stable operation via in situ formation of proton-supplying sites, further quantification of the catalyst’s kd and expected durability is recommended to strengthen its industrial application potential.\n2. The authors used XPS characterization to demonstrate that surface sulfur species remain stable at approximately 3% throughout the reaction without significant accumulation. The mechanism underlying the absence of sulfur overaccumulation should be further clarified.\n3. The authors should present the catalytic performance of Al2O3 catalyst under identical conditions as a reference. Characterization shows that only a single Al–HSO4 species forms on Al2O3, which may enhance activity but not stability. The respective contributions of the proton-supplying sites Al–HSO4 and Ga–HS to catalytic activity and stability should be further elaborated.\n4. In Figure S17, the authors demonstrate the recovery of F- and SO42-, which are produced from the catalytic hydrolysis of CF4 and the catalytic oxidation of SO2, into nearly pure-phase BaSO4 and BaFCl. However, the Methods section lacks a method of the recovery procedure. The authors should provide the experimental details for this aspect of the work.\n5. While SO2/CF4 concentrations match industry, gas hourly space velocity (GHSV=1,000 h-1) is below typical industrial values (>10,000 h-1). Test performance at higher GHSV. Additionally, industrial flue gases often contain HF, CO₂. Testing the impact of these components on catalyst stability is needed, such as add HF to long-term tests in Fig. 1e.\n6. Arrhenius analysis shows 17% Ea reduction (Fig. 1c), but quantitative correlation between proton sites and energy barriers is missing. Recommend DFT calculations comparing C-F bond cleavage barriers at Al–OH vs. Al–HSO4 sites. In addition, peaks at 2900-3400 cm-1 are typically O–H stretches, not free H+. Provide stronger evidence, such as H/D isotope exchange experiments.\n7. In the author's previous work (Angew. Chem. Int. Ed. 2023, e202305651), Ga/θ-Al2O3 already had very high catalytic activity, and no significant deactivation was observed after 1000 h of reaction. I believe that this catalyst will not deactivate even after continuing the reaction up to 2500 h. The author needs to clarify the breakthrough of the SO2 driven strategy, which should not be as simple as just reducing the reaction temperature by 50 ℃. One additional minor suggestion: the colors of -HS and -HSO4 in Figure 2f should be swapped to correspond with those in Figures 2d and 2e。\n8. The author needs to provide more experimental data to support that the introduction of SO2 can inhibit the fluorination of the catalyst conclusion. While XPS negates AlFₓ accumulation, fluorine mass balance is absent (such as total F content in post-reaction catalysts). The proposed disproportionation pathway to +6/-2 sulfur species lacks experimental evidence for intermediates (such as trapped HSO3-). Suggest time-resolved MS to track sulfur evolution. It is suggested that the author provide more DFT calculations and experimental results to clarify the evolution process of sulfur species, thereby perfecting the evidence chain between the formation of proton sites, the reduction of energy barriers, and anti-poisoning."}, "author_response": "A Point-to-Point Response to Reviewer's comments\nDear Editor and Reviewers,\nThank you for taking time and effort to carefully examine our manuscript. Your\ncomments are highly appreciated and helpful in improving this work. We have made\ncorresponding changes to the manuscript (highlighted in yellow) and supporting\ninformation to address the editor's concerns and the requests of the reviewers; these\nchanges are discussed in detail in a point-to-point response to the reviewers' comments,\nas shown below.\nReviewer #1:\nThis work evaluated a strategy for improving CF decomposition performance by\n4\nintroducing SO into a Ga/θ-Al O catalyst. Authors reported that SO addition\n2 2 3 2\nincreased the CF decomposition rate by approximately 90%, reduced the reaction\n4\nactivation energy, and enabled complete decomposition and long-term stable operation\nat a relatively low temperature of 550 °C. However, the following points require further\ndiscussion.\nResponse: We sincerely thank the reviewer for the positive and constructive evaluation\nof our work. In response to the reviewer’s insightful comments, we have thoroughly\nrevised the manuscript and incorporated additional computational and experimental\nanalyses to strengthen the mechanistic understanding and overall scientific robustness\nof the study.\n1. The title uses the plural form \"perfluorocarbons,\" but the experiment focused on CF\n4\nalone. It would be appropriate to add screening results for C F , CHF , and SF as\n2 6 3 6\n1\nsupplementary material, or to specify the title more specifically.\nResponse: We sincerely thank the reviewer for this valuable suggestion. In response,\nwe have investigated the influence of SO introduction on the catalytic decomposition\n2\nperformance of C F and SF . The corresponding results are presented in Fig. R1-2.\n2 6 6\nFor C F decomposition, as shown in Fig. R1, the introduction of SO markedly\n2 6 2\nenhanced the decomposition rate from approximately 20% to over 40% under identical\ntesting conditions, demonstrating a significant promotional effect similar to that\nobserved for CF . However, since the catalytic decomposition of C F involves both C–\n4 2 6\nF and C–C bond cleavage, our preliminary results are insufficient to conclude that SO\n2\npromotes C F decomposition via the same mechanism as in CF hydrolysis.\n2 6 4\nFor SF decomposition, as shown in Fig. R2, the introduction of SO exhibited\n6 2\nnegligible influence, with the decomposition rate remaining at around 15% under both\nconditions. This is likely because the SF decomposition process inherently generates\n6\nsulfur-containing intermediates that already possess promotional effects, rendering\nadditional SO introduction less effective.\nwe have revised the title by changing “perfluorocarbons” to the singular form\n“perfluorocarbon” and clarified in the manuscript that the main focus of this study is on\nCF .\n2 2 6\nAl O . (Reaction temperature: 600 ℃; GHSV: 2000 h-1; C F concentrations: 18000\n2 3 2 6\n2\nppm; SO concentrations: 5000 ppm, if use.)\n2 6\nAl O . (Reaction temperature: 450 ℃; GHSV: 2000 h-1; SF concentrations: 18000 ppm;\n2 3 6\nSO concentrations: 5000 ppm, if use.)\n➢ The corresponding content “Efficient and stable catalytic hydrolysis of\nperfluorocarbon enabled by SO -mediated proton supply” has been revised (Lines 1-2,\n2. While the CF ; adsorption energy at a single Al3+ site is significant, the differences\n4\nin adsorption characteristics across various surface sites on θ-Al O are not considered.\n2 3\nAdditional sites should be considered for comparison of the CF adsorption energy\n4\nresults.\nResponse: We appreciate the reviewer’s insightful comment regarding the diversity of\nadsorption sites on θ-Al O . In our previous work, we have demonstrated that the\n2 3\nsynthesized θ-Al O nanosheets predominantly expose the (010) facet, which is the\n2 3\nmost stable and catalytically relevant surface under our experimental conditions.\nThe θ-Al O consists of approximately 50% tetrahedrally coordinated and 50% octahedrally\n2 3\ncoordinated Al atoms. On the (010) surface, only two types of Al sites are present,\nnamely three-coordinated Al (Al ) and four-coordinated Al (Al ).\nIII IV\nsites are –0.336 eV and –0.140 eV, respectively, indicating that CF preferentially\n4\nadsorbs on the more unsaturated Al sites. These results confirm that the CF\nIII 4\nadsorption characteristics have been comprehensively considered for all accessible\nactive sites on the exposed θ-Al O (010) surface.\n2 3\nE = -0.336 eV E = -0.140 eV\nads ads\nCF adsorbs at the Al site CF adsorbs at the Al site\nFig. R3 Adsorption energy of CF adsorbed on Al and Al sites on the exposed θ-\nAl O (010) surface.\n2 3\nCorresponding revision:\n➢ Fig. R3 have been updated to Supplementary Fig. 16 (Page 17, Revised\nsupplementary information).\n3. While the CF adsorption energy on the Al–HSO surface has been presented, data\n4 4\non the CF adsorption energy on the core catalyst, Ga/θ-Al O surface, is not available.\n4 2 3\nA corresponding calculation is required for direct comparison.\nResponse: We appreciate the reviewer’s insightful suggestion. Our previous study\nconfirmed that Ga modification occurs through substitutional doping at the Al sites,\nIII\nwithout altering the crystal phase or the dominant exposed facet of Al O . Therefore,\n2 3\nthe adsorption behavior of CF on the Ga/θ-Al O catalyst was evaluated using the θ-\n4 2 3\nAl O (010) surface model (Fig. R4).\n2 3\nIII 4\nis much weaker than that on the Al site of pristine θ-Al O . This result indicates that\nIII 2 3\nsurface Ga is not an active site for CF adsorption and activation. After Ga substitution,\nIII 4\nthe adsorption energy on the remaining Al site slightly increases to –0.340 eV, which\nIII\nmay result from Ga-induced modulation of the local electronic structure around the Al\nIII\nsite. In comparison, the CF adsorption energy on Al site with Al–HSO is –0.50 eV,\nhigher than –0.340 eV for the Al site with Ga modification. This finding confirms that\nIII\nthe Al–HSO configuration indeed enhances the adsorption strength of CF on the Al\n4 4 III\nsites, supporting the reliability of our conclusion.\nFig. R4 Adsorption energy of CF adsorbed on Ga and Al sites on the exposed Ga/θ-\nAl O (010) surface.\n2 3\nTable R1 Adsorption energy of CF on θ-Al O and Ga/θ-Al O surfaces.\n4 2 3 2 3\nCatalyst Site CF adsorption energy (eV)\nIII\nθ-Al O\n2 3\nAl -0.140 eV\nIV\nGa/θ-Al O Ga -0.157 eV\n2 3 III\n4\na\nE\nd s\na d\no\\s\n=\n- 0\n. 1\n5\n7\ne\nV\na\nt\nt h\ne\nG\na\nIII\ns i t e C F\n4\na d\nE\ns\na d\no\\s\n=\n- 0\n. 3\n4\n0\ne\nV\na\nt\nt\nh\ne\nA\nl\nIII\ns i t e\nAl -0.340 eV\nIII\nCorresponding revision:\n➢ Fig. R4 have been updated to Supplementary Fig. 17 (Page 18, Revised\nsupplementary information).\n➢ Tab. R1 have been updated to Supplementary Tab. 3 (Page 29, Revised\nsupplementary information).\n➢ The corresponding content “To evaluate the effect of surface Al–HSO sites on the\n4 4\nthe θ-Al O (010) and Ga/θ-Al O (010) surface (Supplementary Figs. 16, 17 and\n2 3 2 3\nSupplementary Table 3). These results indicated that the Al site was the primary\nIII\nadsorption site for CF , and the effect of Ga doping on this site was negligible. The\n4\nintrinsic stability of Al–HSO sites, as well as the influence of SO introduction on its\n4 2\nstructural stability, was further evaluated (Supplementary Figs. 18-20). These results\ndemonstrated that Al–HSO sites was intrinsically stable, and the introduction of SO\n4 2\ndoes not compromise its structural integrity. The CF adsorption energy (E ) on θ-\n4 ads\nAl O –HSO was −0.50 eV, significantly stronger than that on θ-Al O –OH (−0.15 eV),\n2 3 4 2 3\nconfirming that Al–HSO sites significantly enhanced the CF adsorption affinity\n4 4\n(Supplementary Fig. 21 and Supplementary Table 4).” has been revised (Lines 254-265,\nRevised manuscript).\n4. The formation energies of functional groups on the θ-Al O –HSO and θ-Al O –OH\n2 3 4 2 3\nsurfaces are not provided, making it difficult to assess the stability and potential for\nformation of the proposed surface structures.\nResponse: We thank the reviewer for this valuable comment. To address this concern,\nwe have calculated the adsorption energies of the θ-Al O –HSO and θ-Al O –OH\n2 3 4 2 3\nsurfaces, as shown in Fig. R5. The calculated adsorption energies are -2.179 eV for θ-\nAl O –HSO and -1.370 eV for θ-Al O –OH. These results indicate that both θ-Al O –\n2 3 4 2 3 2 3\n4 2 3\nunder the reaction conditions, supporting the structural rationality of the proposed\nsurface models.\nThe adsorption energy of –OH is defined as:\n𝐸 = 𝐸 −𝐸 −𝐸\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝑂𝐻\nwhere E is the total energy of OH adsorbed on the surface, E is the energy of\ntotal slab\nclean surface, E is the energy of the –OH.\nOH\nThe adsorption energy of –HSO is defined as:\n4\n𝐸 = 𝐸 −𝐸 −𝐸\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝐻𝑆𝑂4\nwhere E is the total energy of –HSO adsorbed on the surface, E is the energy of\ntotal 4 slab\nclean surface, E is the energy of the –HSO .\nHSO4 4\nFig. R5 The adsorption energies of –HSO and –OH adsorbed on the exposed θ-Al O\n4 2 3\n(010) surface.\nCorresponding revision:\na\nA\nd s\nl –\n=\n- O\n1 . 3\nH\n7\ns\n0\ni t\ne\ne V E\nA\na d\nl –\ns\nH\n=\nS\n- 2\nO\n.\n4\n1 7\ns\n9\ni t e\ne V\n➢ Fig. R5 have been updated to Supplementary Fig. 18 (Page 19, Revised\nsupplementary information).\n➢ The corresponding content “The adsorption energy of –OH is defined as:\n𝐸 = 𝐸 −𝐸 −𝐸 (4)\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝑂𝐻\nwhere E is the total energy of OH adsorbed on the surface, E is the energy of\ntotal slab\nclean surface, E is the energy of the –OH.\nThe adsorption energy of –HSO is defined as:\n4\n𝐸 = 𝐸 −𝐸 −𝐸 (5)\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝐻𝑆𝑂4\nwhere E is the total energy of –HSO adsorbed on the surface, E is the energy of\ntotal 4 slab\nclean surface, E is the energy of the –HSO .” has been revised (Lines 452-459,\nHSO4 4\nRevised manuscript).\n5. There is no computational basis for verifying the true stability of the Al–HSO and\n2\nresults are required to verify this.\nResponse: We appreciate the reviewer’s valuable suggestion. To verify the true stability\nof the Al–HSO and Ga–HS structures upon SO introduction, we performed adsorption\n4 2\nenergy analyses of H atom adsorption on the Al–SO and Ga–S sites as well as on the\n2\nadsorption on the Al–SO site and on SO are −1.342 eV and −0.335 eV, respectively.\n4 2\nFor the Ga–S site, the corresponding adsorption energies are −1.576 eV and −0.550 eV.\nThe approximately 1 eV difference in adsorption energy between H adsorption on the\nAl–SO or Ga–S sites and on the SO molecule indicates that the introduction of SO\n4 2 2\ndoes not alter the stability of the Al–HSO and Ga–HS structures. These results confirm\n4\nthat both structures remain thermodynamically stable under the reaction conditions.\n𝐸 = 𝐸 −𝐸 −0.5∗𝐸\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝐻2\nwhere E is the total energy of H atom adsorbed on the surface, E is the energy of\ntotal slab\nclean surface, E is the energy of the H molecule.\nH2 2\nE = -1.342 eV E = -0.355 eV\nads ads\nH atom adsorb at Ga–S site H atom adsorb at SO\nads ads\nH atom adsorb at Al–SO site H atom adsorb at SO\n4 2\nFig. R7 The adsorption energies of H atom adsorbed at Al–HSO site and SO ,\n4 2\nrespectively.\n➢ Fig. R6 have been updated to Supplementary Fig. 19 (Page 20, Revised\nsupplementary information).\n➢ Fig. R7 have been updated to Supplementary Fig. 20 (Page 21, Revised\nsupplementary information).\n➢ The corresponding content “The adsorption energies of H atom adsorption is defined\nas:\n𝐸 = 𝐸 −𝐸 −0.5∗𝐸 (6)\n𝑎𝑑𝑠 𝑡𝑜𝑡𝑎𝑙 𝑠𝑙𝑎𝑏 𝐻2\nwhere E is the total energy of H atom adsorbed on the surface, E is the energy of\ntotal slab\nclean surface, E is the energy of the H molecule.” has been revised (Lines 460-463,\nH2 2\nRevised manuscript).\n➢ The corresponding content “To evaluate the effect of surface Al–HSO sites on the\n4 4\nthe θ-Al O (010) and Ga/θ-Al O (010) surface (Supplementary Figs. 16, 17 and\n2 3 2 3\nSupplementary Table 3). These results indicated that the Al site was the primary\nIII\nadsorption site for CF , and the effect of Ga doping on this site was negligible. The\n4\nintrinsic stability of Al–HSO sites, as well as the influence of SO introduction on its\n4 2\nstructural stability, was further evaluated (Supplementary Figs. 18-20). These results\ndemonstrated that Al–HSO sites was intrinsically stable, and the introduction of SO\n4 2\ndoes not compromise its structural integrity. The CF adsorption energy (E ) on θ-\n4 ads\nAl O –HSO was −0.50 eV, significantly stronger than that on θ-Al O –OH (−0.15 eV),\n2 3 4 2 3\nconfirming that Al–HSO sites significantly enhanced the CF adsorption affinity\n4 4\n(Supplementary Fig. 21 and Supplementary Table 4).” has been revised (Lines 254-265,\nRevised manuscript).\n6. The mechanism of the Ga–HS structure donating protons and undergoing\nregeneration after the reaction, as claimed in the experiment, is not supported\n10\ncomputationally. Analysis of the reaction pathway and energy barrier for this process is\nrequired.\nResponse: We thank the reviewer for this insightful comment. To verify the\nregeneration mechanism of the Ga–HS structure after proton donation, we analyzed the\nreaction pathway and energy barrier associated with H O dissociation on the Ga–S site.\nadsorption and dissociation of an H O molecule. Specifically, an H O molecule first\n2 2\nadsorbs onto the neighboring Al site adjacent to the Ga–S site. Subsequently, the O–H\nbond in the H O molecule cleaves, generating an H radical that migrates to the S atom\n2\nof the Ga–S site, forming a new –HS group. The calculated energy profile shows that\nthe O–H bond cleavage is the rate-determining step, with an energy barrier of 0.98 eV.\nThis result indicates that the regeneration of the Ga–HS structure through H O\n2\ndissociation is feasible under the reaction conditions, consistent with the experimental\nobservations.\nFig. R8 Reaction energy profiles and related structures of the Ga–HS structure\n11\nregeneration.\nCorresponding revision:\n➢ Fig. R8 have been updated to Supplementary Fig. 22 (Page 23, Revised\nsupplementary information).\n➢ The corresponding content “In addition, the effect of SO introduction on the stability\n2\nof the Ga–HS site and the regeneration of the Ga–HS site were further analyzed by DFT\ncalculations (Supplementary Fig. 19, 22). The results indicated that the introduction of\nSO does not disrupt the structural integrity of the Ga–HS site, and the regeneration of\n2\nthe Ga–HS structure is feasible (an energy barrier of 0.98 eV).” has been revised (Lines\n272-276, Revised manuscript).\nMinorly, In the main text, “Complete CF and SO conversion over 2,500 hours.”\n4 2\nHowever, according to Supplementary Table S1, the SO conversion is approximately\n2\n95–98%. Authors should be aware of typographical errors such as molar, fourier, etc.\nResponse: We thank the reviewer for carefully pointing out these issues. The phrase\n“Complete CF and SO conversion over 2,500 hours” has been revised to “nearly\n4 2\ncomplete CF and SO conversion” to accurately reflect the experimental results. In\n4 2\naddition, typographical corrections have been made throughout the manuscript,\nincluding changing “molar” to “mol” and “fourier” to “Fourier.” All terminology, units,\nand symbols have been checked and standardized according to the Nature\nCommunications style guide.\nCorresponding revision:\n➢ The corresponding content “Remarkably, the catalyst exhibited outstanding\ndurability, maintaining nearly complete CF and SO conversion over 2,500 hours\n4 2\nwithout any detectable deactivation, demonstrating the robustness and long-term\noperational viability of the system for potential industrial applications.” has been\nrevised (Lines 141-144, Revised manuscript).\n12\n➢ The corresponding content “H SO -modified” represents the catalyst modified by 20%\n2 4\nmol ratio of H SO ” has been revised (Lines 228-229, Revised manuscript).\n2 4\n➢ The corresponding content “corresponding to a Ga mol content of 30%” has been\nrevised (Line 374, Revised manuscript).\n➢ The corresponding content “in situ diffuse reflectance infrared Fourier transform\nspectroscopy (DRIFTS) was conducted” has been revised (Lines 176-177 and 422,\nRevised manuscript).\nThis study reports an innovative approach to achieve efficient and stable CF hydrolysis\n4\nat low temperature through SO -driven in situ formation of proton-supplying sites. The\n2\nwork presents interesting results regarding C–F bond activation, resistance to fluorine\npoisoning and reaction mechanism. Given the significance of developing practical\nstrategies for PFAS degradation under industrially relevant conditions, I find this study\npotentially impactful and recommend it for consideration in Nature Communications.\nHowever, several aspects require further clarification and improvement.\nResponse: We sincerely thank the reviewer for the positive and encouraging evaluation\nof our work. Following the reviewer’s valuable suggestions, we have carefully revised\nthe manuscript to strengthen the mechanistic discussion, expand the comparative\nanalysis of adsorption and formation energies, and provide additional computational\nand experimental results where appropriate. We believe that these revisions\nsignificantly enhance the rigor, clarity, and overall impact of the work.\n1. The deactivation constant (k ) and expected durability are important metrics for\nd\nevaluating the industrial applicability of the catalyst. While the authors report a strategy\nthat enables 2,500 hours of stable operation via in situ formation of proton-supplying\nsites, further quantification of the catalyst’s k and expected durability is recommended\nd\nto strengthen its industrial application potential.\nResponse: We thank the reviewer for this constructive suggestion. To quantitatively\nevaluate the catalyst stability, we calculated the deactivation constant (k ) based on the\nd\ntime-on-stream conversion data according to the first-order deactivation model:\n1−𝑋 1−𝑋\nln( 𝑓 )−ln⁡( 𝑖)\n𝑋 𝑋\n𝑘 (ℎ−1) = 𝑓 𝑖\nd 𝑡\nX is the initial decomposition (%) of CF . X is the final decomposition (%) of CF .\ni 4 f 4\nt is the time throughout the reaction. τ (h): the catalyst life, τ = 1/k .\nd\nThe initial decomposition rate (average value over the first 20 h) was 99.54%, and\nthe final decomposition rate (average value over the last 20 h) was 98.77% (Fig. R9).\ncorresponding to an expected catalyst lifetime of approximately 2,522 h. These results\nconfirm that the catalyst exhibits extremely low deactivation over 2,500 h of operation,\nvalidating the high stability and industrial relevance of the SO -driven in situ proton-\n2\nsupplying strategy.\nFig. R9 Stability test under 550 °C for the CF and SO synergistic reaction over Ga/θ-\n4 2\nAl O catalyst.\n2 3\nCorresponding revision:\n➢ The corresponding content “To quantitatively evaluate the catalyst stability, we\ncalculated the deactivation constant (k ) based on the time-on-stream conversion data\nd\naccording to the first-order deactivation model:\n1−𝑋 1−𝑋\nln( 𝑓 )−ln⁡( 𝑖)\n𝑋 𝑋\n𝑘 (ℎ−1) = 𝑓 𝑖\nd 𝑡\nX is the initial decomposition (%) of CF . X is the final decomposition (%) of CF . t is\ni 4 f 4\nthe time throughout the reaction. τ (h): the catalyst life, τ = 1/k .” has been revised (Lines\nd\n415-420, Revised manuscript).\n➢ The corresponding content “Further, the calculated deactivation constant was\n3.97×10−4 h−1, corresponding to an expected catalyst lifetime of approximately 2,522 h,\nvalidating the long-term practical viability of this system.” has been revised (Lines 145-\n147, Revised manuscript).\n15\n2. The authors used XPS characterization to demonstrate that surface sulfur species\nremain stable at approximately 3% throughout the reaction without significant\naccumulation. The mechanism underlying the absence of sulfur overaccumulation\nshould be further clarified.\nResponse: We thank the reviewer for this valuable comment. The mechanism for the\nabsence of sulfur overaccumulation on the catalyst surface is as follows. First, SO is\n2\nadsorbed on the –OH sites of the catalyst surface to form –HSO - species, which\n3\nsubsequently undergo disproportionation to generate Al–HSO and Ga–HS sites (Fig.\nsurface, and continuous SO introduction does not destroy the structural stability of the\n2\nalready formed Al–HSO and Ga–HS sites (Fig. R6 and R7). Instead, SO are oxidized\n4 2\nby surface oxygen sites of the catalyst to form SO , which is then absorbed by the NaOH\n3\nsolution to form SO 2- ions. The SO conversion remained above 95% throughout 2,500\n4 2\nhours of continuous operation, further confirming that sulfur species do not excessively\naccumulate on the catalyst surface.\nFig. R10 In situ DRIFTS measurements of following SO and CF preadsorption as a\n2 4\nfunction of temperature.\nform form\nH atom adsorb at Ga–S site H atom adsorb at SO\n4 2\nrespectively.\n3. The authors should present the catalytic performance of Al O catalyst under\n2 3\nidentical conditions as a reference. Characterization shows that only a single Al–HSO\n4\nspecies forms on Al O , which may enhance activity but not stability. The respective\n2 3\ncontributions of the proton-supplying sites Al–HSO and Ga–HS to catalytic activity\n4\nand stability should be further elaborated.\nE\na\nfo\nd\nr m\ns o\n=\n-\n1 .\n5\n7\n6\ne\nV\nA\nl\n– S\nO\n4\ns i t e H a\nE\nt o\nfo\nm\nr m\na\n=\n-\n0\n. 5\n5 0\ne V\nS O\nthe θ-Al O catalyst after the co-treatment of CF and SO confirmed the exclusive\n2 3 4 2\nformation of Al–HSO species on the surface. To clarify its role, we further evaluated\n4\nthe catalytic performance of θ-Al O under identical CF + SO reaction conditions. As\n2 3 4 2\nshown in Fig. R11, the introduction of Al–HSO species markedly increased the CF\n4 4\ndecomposition rate from approximately 33% to 60%, demonstrating the strong\npromoting effect of Al–HSO sites on C–F bond activation. However, the activity\n4\ngradually decreased with time on stream, and the CF decomposition rate dropped to\n4\nabout 49% after 75 h. The corresponding deactivation constant was calculated to be\n5.72×10−3 h−1, which is considerably higher than that of the Ga/θ-Al O catalyst\n2 3\n(3.97×10−4 h−1). These results indicate that while the Al–HSO sites significantly\n4\nenhance catalytic activity by providing additional proton-supplying centers for C–F\nbond activation, the Ga–HS sites play a crucial role in defluorination and regeneration\nof the active site, thereby contributing to long-term catalytic stability.\nFig. R11 Stability test under 550 °C for the CF and SO synergistic reaction over θ-\n4 2\nAl O catalyst.\n2 3\n4. In Figure S17, the authors demonstrate the recovery of F- and SO 2-,\n4\nproduced from the catalytic hydrolysis of CF and the catalytic oxidation of SO ,\n4 2\ninto\nnearly pure-phase BaSO and BaFCl. However, the Methods section lacks a method of\n4\nthe recovery procedure. The authors should provide the experimental details for this\n18\naspect of the work.\nResponse: We thank the reviewer for this valuable suggestion. The detailed recovery\nprocedure has now been added to the revised Methods section. Specifically, the tail gas\ngenerated from the CF +SO reaction was first passed through 500 mL of an alkaline\n4 2\nabsorption solution containing 10 g L-1 NaOH. The concentrations of F- and SO 2- ions\n4\nin the resulting solution were determined by ion chromatography.\nTo recover sulfate species, a small amount of dilute HCl solution was added to\nadjust the pH of the absorption solution to 7, followed by the addition of BaCl at a\n2\nstoichiometric ratio of Ba:SO 2- = 1:1 under ambient conditions. After stirring for 30\n4\nmin, the resulting white precipitate was separated by centrifugation, washed three times\nwith deionized water and three times with ethanol, and identified as BaSO .\namount of BaCl was added under stirring for 30 min. The newly formed white\n2\nprecipitate was collected and identified as BaFCl. The XRD patterns confirmed that\nboth BaSO and BaFCl were obtained as nearly pure phases, verifying the effectiveness\n4\nof the by-product recovery process.\nCorresponding revision:\n➢ The corresponding content “Resource recycling. Specifically, the tail gas generated\nfrom the CF +SO reaction was first passed through 500 mL of an alkaline absorption\n4 2\nsolution containing 10 g L-1 NaOH. The concentrations of F- and SO 2- ions in the\n4\nresulting solution were determined by ion chromatography. To recover sulfate species,\na small amount of dilute HCl solution was added to adjust the pH of the absorption\nsolution to 7, followed by the addition of BaCl at a stoichiometric ratio of Ba:SO 2- =\n2 4\n1:1 under ambient conditions. After stirring for 30 min, the resulting white precipitate\nwas separated by centrifugation, washed three times with deionized water and three\ntimes with ethanol, and identified as BaSO . The remaining solution was then heated in\n4\na water bath at 60 °C, and an excess amount of BaCl was added under stirring for 30\n2\nmin. The newly formed white precipitate was collected and identified as BaFCl. The\n4\nphases, verifying the effectiveness of the by-product recovery process.” has been\nrevised (Lines 370-382, Revised manuscript).\n5. While SO /CF concentrations match industry, gas hourly space velocity\n2 4\n(GHSV=1,000 h-1) is below typical industrial values (> 10,000 h-1). Test performance\nat higher GHSV. Additionally, industrial flue gases often contain HF, CO .\nimpact of these components on catalyst stability is needed, such as add HF to long-term\ntests in Fig. 1e.\nResponse: We appreciate the reviewer’s valuable suggestion. To evaluate the catalyst\nperformance under industrially relevant conditions, we conducted additional CF + SO\n4 2\nsynergistic reaction tests at a higher GHSV of 10,000 h-1. As shown in Fig. R12, the\ncatalyst maintained a stable CF decomposition rate of approximately 20%,\n4\ndemonstrating its strong potential for industrial application even below typical\nindustrial conditions.\nIn addition, we investigated the effect of HF, which is commonly present in\nindustrial flue gas, on the stability of the catalyst. The results are shown in Fig. R13.\nAt a reaction temperature of 525 °C, the introduction of 1,000 ppm HF caused no\nobservable change in either CF decomposition rate (approximately 60%) or stability.\n4\nlarge amount of HF. For example, 2,500 ppm CF can generate about 10,000 ppm HF,\n4\nwhich is far higher than the HF concentration typically found in industrial flue gas.\nThese results demonstrate that the developed catalyst performs reliably under\nindustrially relevant conditions and remains resistant to HF-induced deactivation,\nhighlighting its potential for industrial application below typical industrial conditions.\n4 2\nAl O catalyst below typical industrial values (10,000 h-1).\n2 3\nFig. R13 Comparison of CF and SO synergistic reaction with and without HF over\n4 2\nGa/θ-Al O catalyst under 525 °C.\n2 3\n6. Arrhenius analysis shows 17% E reduction (Fig. 1c), but quantitative correlation\na\nbetween proton sites and energy barriers is missing. Recommend DFT calculations\ncomparing C–F bond cleavage barriers at Al–OH vs. Al–HSO sites. In addition, peaks\n4\nat 2900-3400 cm-1 are typically O–H stretches, not free H+.\nProvide stronger evidence,\nsuch as H/D isotope exchange experiments.\nResponse: We thank the reviewer for this valuable comment. The C–F bond cleavage\nbarriers of adsorbed CF were calculated using the climbing image nudged elastic band\n4\n(CI-NEB) method (Fig. R9). For Al–HSO site, C–F bond cleavage barrier is 1.20 eV,\n4\n21\nwith a reaction energy of −2.98 eV. These values are both kinetically and\nthermodynamically more favorable than those of Al–OH site, which has an activation\nbarrier of 1.37 eV and a reaction energy of −2.43 eV. These simulations suggest that\nAl–HSO site is more effective in promoting C−F bond cleavage than that of Al–OH\n4\nsite.\nAlthough H/D isotope exchange experiments could not be conducted at this stage,\nwe have performed additional In situ DRIFTS experiments to verify the assignment of\nthe peaks at 2900–3400 cm–1. As shown in Fig. R14, the physically adsorbed H O\n2\nexhibits a broad band ranging from 2650 to 3650 cm–1, centered at approximately 3400\ncm–1. In contrast, during the CF and SO synergistic reaction, the observed peak\n4 2\ncorresponding to H+ species appears within the range of 2900–3400 cm–1 with a center\nat 3250 cm–1. The distinct difference in both peak position and shape clearly indicates\nthat the feature at 2900–3400 cm–1 cannot be attributed to O–H stretching vibrations of\nadsorbed H O. Moreover, if the 2900–3400 cm–1 band were associated with the O–H\n2\nstretching vibration of H O, a corresponding O–H bending vibration at approximately\n2\n1640 cm–1 would also be expected. However, as shown in Fig. 3b, no such band is\nobserved at 1640 cm–1, further confirming that the 2900–3400 cm–1 peak originates\nfrom the characteristic peak of H+ species rather than the O–H stretching vibration of\nH O.\n2\nbond breakage.\nFig. R14 In situ DRIFTS of CF and SO synergistic reaction and H O adsorption.\n4 2 2\n4 4\nand b) CF and SO synergistic reaction over Ga/θ-Al O catalyst under 550 °C with a\n4 2 2 3\nfunction as time. c) Comparison of H+ peak between solo and synergistic reaction. d)\nThe absorbance of H+ generating with a function as time.\n7. In the author's previous work (Angew. Chem. Int. Ed. 2023, e202305651), Ga/θ-\nAl O already had very high catalytic activity, and no significant deactivation was\n2 3\nobserved after 1000 h of reaction. I believe that this catalyst will not deactivate even\nafter continuing the reaction up to 2500 h. The author needs to clarify the breakthrough\nof the SO driven strategy, which should not be as simple as just reducing the reaction\n2\ntemperature by 550 °C. One additional minor suggestion: the colors of -HS and -HSO\n4\nin Figure 2f should be swapped to correspond with those in Figures 2d and 2e.\nResponse: We thank the reviewer for this insightful and constructive comment. The\n24\na\n).u.a(\necnabrosbA\nc\n).u.a(\necnabrosbA\n3\n5.0\n4\n50.0\n0 0\n3 4\n3\n0\n2\n0\n0 0 3 0W\nW\n0 0a\nH\n3a\nv e n\n+\n2 0 0\nv e n\n1u\nu\n6m\nm\nH\n0 0b\nb\nC\nO\n2\n1 4 0 0\ne rs (c\n3 0 0 0\ne rs (c\nF\n1m\nm\n4\n2 0 0\n– 1 )\n– 1 )\n1 0\nC\nS\nC\n2\nO\nF\n8\n0\n+ 4\n2\n4\n0 0\nC F\n0 0\nO\n4\n2\n8\n0\n0 m in\nm in\nb\n).u.a(\necnabrosbA\nd\n).u.a(\necnabrosbA\n5.0\n3 4 0\n+ H\n0\n3 2\n+3\n2 2\n0 0\n6\n3 0 0\nW\n2 0\n0a\nv e\nH\nn\nT\nS O 1 3 7 9 C F 2\nC F\n4\n1 2 7 9s\nu lfa te\nO\n2 1 4 6 0\n1 5 6 6\n1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0\n– 1 u m b e rs (c m )\nC F + S O\n4 2\n4 0 6 0\nim e (m in )\n+4\n8\n0 0\nC F\n2\n0\n8\n0\n0 m in\nm in\nbreakthrough of the SO -driven strategy lies in transforming SO , which is traditionally\n2 2\nregarded as a catalyst poison, into a reactive promoter that simultaneously enhances\nboth catalytic activity and stability. In the revised manuscript, we have provided a more\nsystematic mechanistic elucidation of this process. Specifically, SO is first activated\n2\non the catalyst surface to form –HSO - intermediates, which subsequently undergo\n3\ndisproportionation to generate Al–HSO and Ga–HS sites. The Al–HSO sites\n4 4\nsignificantly increase the CF adsorption energy and lower the C–F bond dissociation\n4\nbarrier, while the Ga–HS sites facilitate defluorination by reducing the Al–F bond\ncleavage barrier and suppressing fluorine accumulation on the catalyst surface. As a\nresult, the SO -driven strategy markedly enhances both the catalytic activity and long-\n2\nterm stability of CF hydrolysis.\n4\nat 550 °C in this work is lower than all previously reported temperatures for full CF\n4\ndecomposition, underscoring the breakthrough of the SO -driven strategy in achieving\n2\nhigh activity at low temperature.\nIn terms of stability, our previous study demonstrated 1,000 h of stable operation\nat 600 °C, whereas the present work achieves 2,500 h of continuous stability at 550 °C.\nAs shown in Fig. 4e, decreasing the reaction temperature significantly increases the\nextent of F-poisoning. Therefore, maintaining 2,500 h of stable operation under low-\ntemperature conditions further demonstrates the novelty of this SO -driven strategy.\n4\nswapped to correspond with those in Fig. 2d and 2e.\nand used Ga/θ-Al O catalysts (testing under 5,000 ppm SO and 2,500 ppm CF for 10\n2 3 2 4\nh). b) TEM images and EDX mapping of the used Ga/θ-Al O catalyst. c) In situ\n2 3\nDRIFTS of CF and SO synergistic reaction without H O over Ga/θ-Al O catalyst\n4 2 2 2 3\nunder 550 °C as a function of time. d) and e) XPS spectra of S 2p for the used Ga/θ-\nAl O catalysts during the CF and SO synergistic reaction under different SO\n2 3 4 2 2\nconcentration (250 – 20,000 ppm) and after different treatments (“-used” represents the\ncatalyst obtained after testing under SO and CF ; “-SO treated” represents the catalyst\n2 4 2\nobtained after testing under SO only; “H SO -modified” represents the catalyst\n2 2 4\nmodified by 20% molar ratio of H SO ). f) The proportion of –HS and –HSO species,\n2 4 4\nas well as the total amount of sulfur species on the catalysts surface as a function of\nSO concentration.\n2\n8. The author needs to provide more experimental data to support that the introduction\nof SO can inhibit the fluorination of the catalyst conclusion. While XPS negates AlF\n2 3\naccumulation, fluorine mass balance is absent (such as total F content in post-reaction\ncatalysts). The proposed disproportionation pathway to +6/-2 sulfur species lacks\nexperimental evidence for intermediates (such as trapped HSO -). Suggest time-\n3\nresolved MS to track sulfur evolution. It is suggested that the author provide more DFT\n26\n).u.a(\nytisnetnI\n).u.a(\nytisnetnI\nS O -treated 2\nfresh sam ple\n10 20 30\n20000 ppm SO 2\n5000 ppm SO 2\n2000 ppm SO 2\n500 ppm SO 2\n175 170B\n40 50 60\n2 θ (d e g re e )\nA l‒H SO 4\n165 160 inding energy (eV )\nG a‒H\n80\n2p\nS\n155\n).u.a(\necnabrosbA\n1400\n1000\ne rs (cm ‒1)\nC F +SO 4 2\n‒H S\n800\n75 m in\n1 m in\n175 170 165 160 155\nCF4+SO2-θ-Al2O3-used\nSO4 2-/Ga/θ-Al2O3\nSO2-Ga/θ-Al2O3-used\nCF4+SO2-Ga/θ-Al2O3-used\nBinding energy (eV)\n).u.a(\nytisnetnI\na b c\nd e S 2p f\n).u.a(\nytisnetnI\n1.0\n0.8\n0.6\n0.4\n0.2\n0.0\n-H\n500C\n-H S O\n1000\no n ce n\nTotal sulfur 4\n2000 5000 10000\ntra tio n o f S O 2\n20000\n4\n3\n2\n1\n0\n)S(\ntnetnoC\ncalculations and experimental results to clarify the evolution process of sulfur species,\nthereby perfecting the evidence chain between the formation of proton sites, the\nreduction of energy barriers, and anti-poisoning.\nResponse: We thank the reviewer for these important suggestions. We will reply to\neach one.\n(1) Total F content in post-reaction catalysts:\nTotal F content in post-reaction catalysts was characterized by Ion\nChromatography (IC, Thermo Scientific ICS-600 Ion Chromatography System). First,\n20 mg of post-reaction catalyst was added to 10% wt of NaOH solution, stirring well\nuntil the solution is completely clear. The F content of the obtained solution was\ndetected by IC (Fig. R15). The F content of the obtained solution were 0.475 mg/L and\n0.117 mg/L by calculation for the CF and CF +SO reaction, respectively. The\n4 4 2\ncorresponding mol ratio of F in catalyst were 2.6% and 0.6% for the CF and CF +SO\n4 4 2\nreaction, respectively. The results confirmed the introduction of SO can inhibit the\n2\nfluorination of the catalyst.\narea. (c) The IC spectra of the used catalysts. (d) Total F content of the used catalysts.\n(2) Experimental evidence for HSO - intermediates:\n3\nsitu DRIFTS to verify the proposed disproportionation pathway and the HSO -\n3\nintermediates. As shown in Fig. R10, after SO pre-adsorption, the depletion of Al–OH\n2\ngroups (3650 – 3750 cm⁻1) and the formation of HSO ⁻ species (1200 and 966 cm⁻1)\n3\nindicated that SO was activated via interaction with surface hydroxyls. As the reaction\n2\ntemperature increased above 250 °C, the transition of HSO ⁻ to SO 2⁻ (1371 and\n3 4\n995 cm⁻1), HSO ⁻ (1190 cm⁻1) and S2- species (688 cm⁻1) were observed. These results\n4\nprovide direct experimental evidence supporting the intermediate (HSO ⁻) formation\n3\nand subsequent transformation of HSO - during the disproportionation process.\n3\n2 4\nfunction of temperature.\n(3) The evidence chain:\nIn the revised manuscript, we have systematically clarified the evidence chain of\nthe SO -driven strategy. The full evidence chain is as follows:\n2\ni) In situ formation of proton-supplying sites\nIn situ DRIFTS of CF +SO pre-adsorption provide direct experimental evidence\n4 2\nsupporting the intermediate (HSO ⁻) formation and subsequent transformation of\n3 4\ndemonstrated the In situ formation of Al–HSO and Ga–HS sites on the catalyst surface.\n4\nii) Effect of SO on the structural stability of the proton-supplying sites\n4 2\nintroduction, we performed formation energy analyses of H atom adsorption on the Al–\nSO and Ga–S sites as well as on the SO molecule. As shown in Figs. R6 and R7, the\n4 2\ncalculated formation energies of H adsorption on the Al–SO site and on SO are −1.342\n4 2\neV and −0.335 eV, respectively. For the Ga–S site, the corresponding formation\nenergies are −1.576 eV and −0.550 eV. The approximately 1 eV difference in formation\nenergy between H adsorption on the Al–SO or Ga–S sites and on the SO molecule\n4 2\nindicates that the introduction of SO does not alter the stability of the Al–HSO and\n2 4\nGa–HS structures. These results confirm that both structures remain\n29\nthermodynamically stable under the reaction conditions.\niii) Al–HSO sites facilitating C–F bond cleavage\n4 ads 2 3 4\nstronger than that on θ-Al O –OH (−0.15 eV), confirming that Al–HSO sites\n2 3 4\nsignificantly enhanced the CF adsorption affinity. The C–F bond cleavage barriers of\n4\nadsorbed CF were calculated using the climbing image nudged elastic band (CI-NEB)\n4\nmethod (Fig. R9). For Al–HSO site, C–F bond cleavage barrier is 1.20 eV, with a\n4\nreaction energy of −2.98 eV. These values are both kinetically and thermodynamically\nmore favorable than those of Al–OH site, which has an activation barrier of 1.37 eV\nand a reaction energy of −2.43 eV. These simulations suggest that Al–HSO site is more\n4\neffective in promoting C−F bond cleavage than that of Al–OH site.\niv) Ga–HS sites facilitating the defluorination of Al–F bonds\nThe energy barrier for HF elimination from fluorinated Ga sites was dramatically\nreduced from 2.34 eV (with Ga–OH) to 0.32 eV with Ga–HS sites, demonstrating the\ncritical role of Ga–HS proton-supplying sites in promoting defluorination and\novercoming fluorine poisoning. Total F content in post-reaction catalysts was\ncharacterized by IC. The corresponding mol ratio of F in catalyst were 2.6% and 0.6%\nfor the CF and CF +SO reaction, respectively. The results confirmed the introduction\n4 4 2\nof SO can inhibit the fluorination of the catalyst.\nSO -driven strategy from four complementary aspects.\n2\nand used Ga/θ-Al O catalysts (testing under 5,000 ppm SO and 2,500 ppm CF for 10\n2 3 2 4\nh). b) TEM images and EDX mapping of the used Ga/θ-Al O catalyst. c) In situ\n2 3\nDRIFTS of CF and SO synergistic reaction without H O over Ga/θ-Al O catalyst\n4 2 2 2 3\nunder 550 °C as a function of time. d) and e) XPS spectra of S 2p for the used Ga/θ-\nAl O catalysts during the CF and SO synergistic reaction under different SO\n2 3 4 2 2\nconcentration (250 – 20,000 ppm) and after different treatments (“-used” represents the\ncatalyst obtained after testing under SO and CF ; “-SO treated” represents the catalyst\n2 4 2\nobtained after testing under SO only; “H SO -modified” represents the catalyst\n2 2 4\nmodified by 20% molar ratio of H SO ). f) The proportion of –HS and –HSO species,\n2 4 4\nas well as the total amount of sulfur species on the catalysts surface as a function of\nSO concentration.\n2\n31\n).u.a(\nytisnetnI\n).u.a(\nytisnetnI\nS O -treated 2\nfresh sam ple\n10 20 30\n20000 ppm SO 2\n5000 ppm SO 2\n2000 ppm SO 2\n500 ppm SO 2\n175 170B\n40 50 60\n2 θ (d e g re e )\nA l‒H SO 4\n165 160 inding energy (eV )\nG a‒H\n80\n2p\nS\n155\n).u.a(\necnabrosbA\n1400\n1000\ne rs (cm ‒1)\nC F +SO 4 2\n‒H S\n800\n75 m in\n1 m in\n175 170 165 160 155\nCF4+SO2-θ-Al2O3-used\nSO4 2-/Ga/θ-Al2O3\nSO2-Ga/θ-Al2O3-used\nCF4+SO2-Ga/θ-Al2O3-used\nBinding energy (eV)\n).u.a(\nytisnetnI\na b c\nd e S 2p f\n).u.a(\nytisnetnI\n1.0\n0.8\n0.6\n0.4\n0.2\n0.0\n-H\n500C\n-H S O\n1000\no n ce n\nTotal sulfur 4\n2000 5000 10000\ntra tio n o f S O 2\n20000\n4\n3\n2\n1\n0\n)S(\ntnetnoC\nE = -1.342 eV E = -0.355 eV\nform form\nH atom adsorb at Ga–S site H atom adsorb at SO\n4 2\nrespectively.\nE\na\nfo\nd\nr m\ns o\n=\n-\n1 .\n5\n7\n6\ne\nV\nA\nl\n– S\nO\n4\ns i t e H a\nE\nt o\nfo\nm\nr m\na\n=\n-\n0\n. 5\n5 0\ne V\nS O\nbond breakage.\nReaction free energy profile for the regeneration of active sites with assistance of Ga–OH and Ga–\nSH sites. In situ DRIFTS of regeneration of active sites for c) CF and SO synergistic reaction and\n4 2\nd) CF solo over Ga/θ-Al O catalyst under 550 °C, respectively. e) Al–OH relative intensity for\n4 2 3\nCF solo and CF and SO synergistic reaction as function with time. In situ Raman spectra testing\n4 4 2\nfor f) CF solo and g) CF and SO synergistic reaction over Ga/θ-Al O catalyst under 550 °C,\n4 4 2 2 3\nrespectively. h) The regeneration rate of active sites on –OH sites and –SH sites.\n34\na\nG a ‒\nG a ‒\nc\n1.0\n0 m in\n).u.a(\nnoitprosbA\n1 1 0 m\n4000\nf\nG a‒O\n).u.a(\nytisnetnI\nS\nin\nH\nH\nI.S .\n-O H s ig n a ls\n3800 3600\nW a v e n u m b e rs (c\nF resh P oisoning\nR egeneration\n400 600\nR a m a n s h ift (c m\nC F + S O flow 4 2\nw ater vapor\n3400\n‒1 m )\nC F + S O 4 2\nA l‒O\n800 1000\n‒1)\nT .S .\nd\n1.0\n0 m in\n).u.a(\nnoitprosbA\n1 1 0 m\n4000\ng\nG a‒O\n).u.a(\nytisnetnI\n200\nin\nF .S .\n-O H s ig n a ls C F flow 4\nw ater vapor\n3800 3600 3400\n‒1 W a v e n u m b e rs (c m )\nF resh C F 4 P oisoning\nA l‒O R egeneration\n400 600 800 1000\n‒1 R a m a n s h ift (c m )\n)Ve(\neliforp\nygrene\neerF\n)%(\ntnuoma\nevitaler\nHO-\n)%(\netar\nnoitarenegeR\nb\n2.5\n2.0\n1.5\n1.0\n0.5\n0.0\ne100\n80\n60\n40\n20\n0\nh\n100\n80\n60\n40\n20\n0\nG a O H –\nG a ‒ S H\n1 2\nC F +S O 4 2\nC F 4\noisoning process\n20 40T\n37%\n‒ O H s ite\nC\nim\n2.34 eV\n0.32 eV\n3 4\nV (Å )\n1 0 0 %\n4 9\nR egeneration process\n60 80 100\ne (m in )\n100%\n‒ S H s ite\n%"}, {"round": 2, "reviewer_comments": {"reviewer_1": "Authors adequately answered all questions raised by the reviewer and the manuscript is clear and publishable now. Thus, I recommend it to be accepted for the publication.", "reviewer_2": "The authors did a very good job of addressing my concerns, performed additional experiments. For example, the study added an investigation into the effect of HF presence on catalyst activity, which further confirms the reliability of this catalyst in industrial applications. In addition, the authors also proved the existence of HSO₃⁻ through in-situ infrared spectroscopy and supplemented the data on the F content in the catalyst after the reaction. I was impressed by the extra work that they performed and greatly appreciate their taking my comments and those of the other reviewers seriously. I have confirmed that the paper has been appropriately revised, and is now acceptable for the publication."}, "author_response": ""}]

Decision letter