Insights into SnO₂ Nanoparticles Supported on Fibrous Mesoporous Silica for CO Catalytic Oxidation

Round 1

Reviewer 1 Report

The authors have synthesized several supports onto which Sn was deposited. The interesting morphology of the supports have enabled the authors to obtain highly active catalysts in CO oxidation. The manuscript is well written, logical and clearly shows that although the state of Sn on the surface is amorphous for both KCC and MCM, the topography of these two differs substantially and impacts the activity of the resulting catalytic systems. The authors also investigated the impact of the Sn loading on the activity and found the optimum value. I recommend the manuscript to be published after minor revisions.

1) The literature is lacking a list of studies of supported metal catalyst. Although they are expensive, they are the main source of information regarding the catalytic oxidation of CO and therefore only mentioning them ignores most of the insight gained thus far on the topic. Please incorporate the studies and findings regarding other catalytic systems than just a handful of oxide catalysts and give a wider context than just SnO_x.

2) Can the authors identify a reason for the worse performance on Sn10 in comparison to Sn7? The characterization data do not show any specific change to which this loss can be attributed, i.e., the decrease of the surface area is gradual with increased loading, there is not much change in the diffraction pattern between Sn7 and Sn10 and considering the fact the DFT results are interpreted as: “The results indicated that CO can be easily adsorbed  on the surface of 7% SnO₂ addition Sn7@KCC-1 catalyst surface and formed active intermediates” then Sn10 could potentially form more of the active intermediates. Please provide a plausible explanation for the drop of the activity upon the increase of the loading from 7 to 10.

3) The manuscript should be proof read to weed out linguistic issues such as:

Line 16 “SnO₂ existed on KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between” should be rephrased

Line 28 “Wherein,” should be “wherein,”

Line 191: “indicating that an excellent stability” should be changed to “indicating an excellent stability”

Line 292: “that they can be effective activated by the catalyst surface” should be changed to “that they can be effectively activated by the catalyst surface”

The English is overall very good, except for some minor issues as the ones indicated above.

Author Response

Response to Reviewer 1

Dear Editor and Reviewers,

Thank you for giving the opportunity to modify the paper again, and we also thank the reviewers for the insightful comments regarding the manuscript # Manuscript ID: Catalysts-2457773 entitled “Insights into SnO₂ nanoparticles supported on fibrous meso-porous silica for CO catalytic oxidation”. Those comments are valuable and very helpful in improving the quality of the work. We have studied the comments carefully and have made corrections (Modified in red). We expect that the revised manuscript can meet the criteria of Catalysts A point-to-point response to reviewers’ comments is shown below.

 

 

Reviewer 1

The authors have synthesized several supports onto which Sn was deposited. The interesting morphology of the supports have enabled the authors to obtain highly active catalysts in CO oxidation. The manuscript is well written, logical and clearly shows that although the state of Sn on the surface is amorphous for both KCC and MCM, the topography of these two differs substantially and impacts the activity of the resulting catalytic systems. The authors also investigated the impact of the Sn loading on the activity and found the optimum value. I recommend the manuscript to be published after minor revisions.

1) The literature is lacking a list of studies of supported metal catalyst. Although they are expensive, they are the main source of information regarding the catalytic oxidation of CO and therefore only mentioning them ignores most of the insight gained thus far on the topic. Please incorporate the studies and findings regarding other catalytic systems than just a handful of oxide catalysts and give a wider context than just SnO_x.

2) Can the authors identify a reason for the worse performance on Sn10 in comparison to Sn7? The characterization data do not show any specific change to which this loss can be attributed, i.e., the decrease of the surface area is gradual with increased loading, there is not much change in the diffraction pattern between Sn7 and Sn10 and considering the fact the DFT results are interpreted as: “The results indicated that CO can be easily adsorbed  on the surface of 7% SnO₂ addition Sn7@KCC-1 catalyst surface and formed active intermediates” then Sn10 could potentially form more of the active intermediates. Please provide a plausible explanation for the drop of the activity upon the increase of the loading from 7 to 10.

3) The manuscript should be proof read to weed out linguistic issues such as:

Line 16 “SnO₂ existed on KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between” should be rephrased

Line 28 “Wherein,” should be “wherein,”

Line 191: “indicating that an excellent stability” should be changed to “indicating an excellent stability”

Line 292: “that they can be effective activated by the catalyst surface” should be changed to “that they can be effectively activated by the catalyst surface”

1) The literature is lacking a list of studies of supported metal catalyst. Although they are expensive, they are the main source of information regarding the catalytic oxidation of CO and therefore only mentioning them ignores most of the insight gained thus far on the topic. Please incorporate the studies and findings regarding other catalytic systems than just a handful of oxide catalysts and give a wider context than just SnO_x.

Response 1: Thank you very much for the comments of this reviewer. The list of studies of supported metal catalyst was added to the Introduction. (please see section of Introduction in the Manuscript)

Platinum group metals (PGMs), such as Pt, Pd, and Rh, have been widely used as critical active components in emission control catalysts, such as three-way catalysts (TWCs). [5] Among the PGMs, Pt-based catalysts have attracted much attention owing to the excellent conclusive activity for CO and hydrocarbons (HCs) oxidation. [6, 7]

Reference

[5] Twigg, M.V. Catalytic control of emissions from cars, Catal. Today. 2011, 163, 33–41.

[6] Tan, W. Alsenani, H. Xie, S.H. Cai, Y.D. Xu, P. Liu, A.N. Ji, J.W. Gao, F. Dong, L. Chukwu, E. Yang, M. Liu, F.D. Tuning Single-atom Pt₁-CeO₂ catalyst for efficient CO and C₃H₆ oxidation: Size effect of ceria on Pt structural evolution. ChemNanoMat. 2020, 6, 1797-1805.

[7] Xin, Y. Zhang, N.N. Lv, Y.N. Wang, J. Li, Q. Zhang, Z.L. From nanoparticles to single atoms for Pt/CeO₂: synthetic strategies, characterizations and applications. J. Rare Earth 2020, 38, 850–862.

2) Can the authors identify a reason for the worse performance on Sn10 in comparison to Sn7? The characterization data do not show any specific change to which this loss can be attributed, i.e., the decrease of the surface area is gradual with increased loading, there is not much change in the diffraction pattern between Sn7 and Sn10 and considering the fact the DFT results are interpreted as: “The results indicated that CO can be easily adsorbed on the surface of 7% SnO₂ addition Sn7@KCC-1 catalyst surface and formed active intermediates” then Sn10 could potentially form more of the active intermediates. Please provide a plausible explanation for the drop of the activity upon the increase of the loading from 7 to 10.

Response 2: Thank you for the reviewer’s insightful comments. High content of active components will lead to aggregation, resulting in the covering of the active site, and thus reduce its catalytic activity to CO, which is also shown in some reported catalysts. (Feng et al., 2020; Wang et al. 2021)

Reference

Feng, B.; Shi, M.; Liu, J. X.; Han, X. C.; Lan, Z. J.; Gu, H. J.; Wang, X. X.; Sun, H. M.; Zhang, Q. X; Li, H. X.; Y. Wang, Li, H. An efficient defect engineering strategy to enhance catalytic performances of Co₃O₄ nanorods for CO oxidation, J. Hazard. Mater., 2020, 394, 122540.

Wang, Y.; Liu, C.; Liao, X.; Liu, Y.; Hou, J.; Pham-Huu, C. Enhancing oxygen activation on high surface area Pd-SnO₂ solid solution with isolated metal site catalysts for catalytic CH₄ combustion, Appl. Surf. Sci. 2021, 564, 150368.

3) The manuscript should be proof read to weed out linguistic issues such as:

Line 16 “SnO₂ existed on KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between” should be rephrased

Line 28 “Wherein,” should be “wherein,”

Line 191: “indicating that an excellent stability” should be changed to “indicating an excellent stability”

Line 292: “that they can be effective activated by the catalyst surface” should be changed to “that they can be effectively activated by the catalyst surface”

Response 3: Thank you very much for pointing out this issue. We have carefully revised the manuscript. In addition, it has been polished by native English speakers, and the polishing report is as follows.

Reviewer 2 Report

Li et al. show in their manuscript a faciale preparation route via solvothermal synthesis to obtain SnO2 nanoparticles supported on KCC-1 resp. MCM-41 for CO oxidation. Several characterisation methods (P-XRD, BET, TPR, DRIFTS) in combination with DFT calculations were applied to propose a reaction mechanism for CO oxidation over SnO2.

General remarks:

- English has to be improved

- In the introduction it is not explained, why (pure) SnO2 is used as active species for CO oxidation. The mentioned two examples treat with promotion effects of Sn for other active metals like Pd or Co. Therefore, examples for Sn as active species in CO oxidation should be provided.

- The development of the reaction mechanism presented is not fully comprehensible - especially the connection between the DRIFTS results with the results of the DFT calculations.

- The term "confined" seems to be missleading, since the Sn-species are not implemeted in pores (at least this conclusion can not be obtained through the used characterisation methods). 

- catalytic activity and DFT calculations were carried out solely for KCC-1, but results of MCM-41 are missing. Why is this (MCM-41) system shown in the manuscript?

- Graphs of P-XRD and ads/des-isotherms are not detailed enough - the discussed features can not be seen in the presented figures.

The English has to be improved several points - mainly grammar.

Author Response

Response to Reviewer 2

Dear Editor and Reviewers,

Thank you for giving the opportunity to modify the paper again, and we also thank the reviewers for the insightful comments regarding the manuscript # Manuscript ID: Catalysts-2457773 entitled “Insights into SnO₂ nanoparticles supported on fibrous meso-porous silica for CO catalytic oxidation”. Those comments are valuable and very helpful in improving the quality of the work. We have studied the comments carefully and have made corrections (Modified in red). We expect that the revised manuscript can meet the criteria of Catalysts A point-to-point response to reviewers’ comments is shown below.

 

 

Reviewer 2

Li et al. show in their manuscript a faciale preparation route via solvothermal synthesis to obtain SnO2 nanoparticles supported on KCC-1 resp. MCM-41 for CO oxidation. Several characterisation methods (P-XRD, BET, TPR, DRIFTS) in combination with DFT calculations were applied to propose a reaction mechanism for CO oxidation over SnO2.

General remarks:

- English has to be improved

- In the introduction it is not explained, why (pure) SnO2 is used as active species for CO oxidation. The mentioned two examples treat with promotion effects of Sn for other active metals like Pd or Co. Therefore, examples for Sn as active species in CO oxidation should be provided.

- The development of the reaction mechanism presented is not fully comprehensible - especially the connection between the DRIFTS results with the results of the DFT calculations.

- The term "confined" seems to be missleading, since the Sn-species are not implemeted in pores (at least this conclusion can not be obtained through the used characterisation methods). 

- catalytic activity and DFT calculations were carried out solely for KCC-1, but results of MCM-41 are missing. Why is this (MCM-41) system shown in the manuscript?

- Graphs of P-XRD and ads/des-isotherms are not detailed enough - the discussed features can not be seen in the presented figures.

1) English has to be improved

Response 1: Thank you very much for pointing out this issue. We have carefully revised the manuscript, and at the same time, it has been polished by native English speakers, and the polishing report is as follows.

2) In the introduction it is not explained, why (pure) SnO2 is used as active species for CO oxidation. The mentioned two examples treat with promotion effects of Sn for other active metals like Pd or Co. Therefore, examples for Sn as active species in CO oxidation should be provided.

Response 2: Thank you very much for this reviewer’s careful correction. The examples for Sn as active species in CO oxidation have been be provided in the manuscript.

Peng et al., [15] demonstrates that mesporous SnO₂ nanosheet materials with a higher surface area, larger pore volume, and more active surface oxygen species showed excellent catalytic activity for CO oxidation.

Reference

[15] Peng, H.G. Peng, Y. Xu, X.L. Fang, X.Z. Liu, Y. Cai, J.X. Wang X. SnO₂ nano-sheet as an efficient catalyst for CO oxidation. Chinese J Catal. 2015, 36(11), 2004-2010.

3) The development of the reaction mechanism presented is not fully comprehensible-especially the connection between the DRIFTS results with the results of the DFT calculations.

Response 3: Thank you for the reviewer’s insightful comments. In this study, Only the adsorbed CO species on the catalyst surface were detected by in situ DRIFTS. Thus, the method of DFT calculation was used to rationally speculate and improve the in situ DRIFTS results, and then the CO catalytic removal path on the SnO₂ catalyst surface was established, which is what DFT computing is good at.

4) The term "confined" seems to be missleading, since the Sn-species are not implemeted in pores (at least this conclusion can not be obtained through the used characterisation methods).

Response 4: Thank you very much for pointing out this issue. We have modified the unreasonable expression in Manuscript. (please see corresponding section of the Manuscript)

5) catalytic activity and DFT calculations were carried out solely for KCC-1, but results of MCM-41 are missing. Why is this (MCM-41) system shown in the manuscript?

Response 5: Thank you for the reviewer’s insightful comments. As mentioned in our introduction, MCM-41 is a carrier material that has been studied more frequently, and it is introduced in this paper as a contrast catalyst. It is obvious that KCC-1 supported catalysts exhibit better CO removal performance.

6) Graphs of P-XRD and ads/des-isotherms are not detailed enough-the discussed features can not be seen in the presented figures.

Response 6: Thank you very much for the reviewer’s careful correction. We have modified Graphs of P-XRD and ads/des-isotherms to make it clearer. (please see Figure 3 and Figure 5 in the Manuscript)

Reviewer 3 Report

Review (major revision):

In the manuscript titled; “Insights into SnO2 nanoparticles confined on fibrous mesoporous silica for CO catalytic oxidation” by Li et al., the authors loaded SnO₂ on two different SiO₂ supports. They found the novel material, KCC-1, presents superior activity.

Introduction:

Some minor improvements in English are necessary. For instance, the authors use the phrase “sintering agglomeration”. These are two different phenomena.

Discussion:

The authors state that according to the results of catalytic tests, there was a good “coupling between active component SnO₂ and KCC-1 supporter”. The authors should elaborate on this further. How was this evident?

The authors loaded the support with 10 wt% of SnOx. This is a significant loading. Do the authors assume, that even at this high loading, SnOx would remain completely dispersed and not show up on XRD?

If all the materials show excellent dispersion, why does Sn10-KCC show less activity than Sn7-KCC?

The sorption curves for the materials are strange. The MCM-based materials should present a drastically different sorption curve. (https://www.acsmaterial.com/mcm-41.html)

In H2-TPR curves, if we assume a 7 wt.% loading, and that a similar mass of the sample was measured, the area of the reduction peak should be 7 % of the area for the pure SnO₂. What is the author's explanation for the discrepancy?

Conclusion:

 

The conclusion part is well written.

The authors should significantly improve the English in the present manuscript. The manuscript has inappropriate phrases, such as;

- "catalyst surface active component"

- "H₂-TPR was constructed to gain insight

- formation of oxygen vacancy structure

Author Response

Response to Reviewer 3

Dear Editor and Reviewers,

Thank you for giving the opportunity to modify the paper again, and we also thank the reviewers for the insightful comments regarding the manuscript # Manuscript ID: Catalysts-2457773 entitled “Insights into SnO₂ nanoparticles supported on fibrous meso-porous silica for CO catalytic oxidation”. Those comments are valuable and very helpful in improving the quality of the work. We have studied the comments carefully and have made corrections (Modified in red). We expect that the revised manuscript can meet the criteria of Catalysts A point-to-point response to reviewers’ comments is shown below.

 

 

Reviewer 3

In the manuscript titled; “Insights into SnO2 nanoparticles confined on fibrous mesoporous silica for CO catalytic oxidation” by Li et al., the authors loaded SnO₂ on two different SiO₂ supports. They found the novel material, KCC-1, presents superior activity.

Introduction:

Some minor improvements in English are necessary. For instance, the authors use the phrase “sintering agglomeration”. These are two different phenomena.

Discussion:

The authors state that according to the results of catalytic tests, there was a good “coupling between active component SnO₂ and KCC-1 supporter”. The authors should elaborate on this further. How was this evident?

The authors loaded the support with 10 wt% of SnOx. This is a significant loading. Do the authors assume, that even at this high loading, SnOx would remain completely dispersed and not show up on XRD?

If all the materials show excellent dispersion, why does Sn10-KCC show less activity than Sn7-KCC?

The sorption curves for the materials are strange. The MCM-based materials should present a drastically different sorption curve. (https://www.acsmaterial.com/mcm-41.html)

 

In H2-TPR curves, if we assume a 7 wt.% loading, and that a similar mass of the sample was measured, the area of the reduction peak should be 7 % of the area for the pure SnO₂. What is the author's explanation for the discrepancy?

 

Conclusion:

 

The conclusion part is well written.

 

Comments on the Quality of English Language

The authors should significantly improve the English in the present manuscript. The manuscript has inappropriate phrases, such as;

- "catalyst surface active component"

- "H₂-TPR was constructed to gain insight

- formation of oxygen vacancy structure

 

1) Some minor improvements in English are necessary. For instance, the authors use the phrase “sintering agglomeration”. These are two different phenomena.

Response 1: Thank you very much for pointing out this issue. We have carefully revised the manuscript, and at the same time, it has been polished by native English speakers, and the polishing report is as follows.

2) The authors state that according to the results of catalytic tests, there was a good “coupling between active component SnO₂ and KCC-1 supporter”. The authors should elaborate on this further. How was this evident?

Response 2: Thank you very much for this reviewer’s careful correction. We have revised the unreasonable statement in the article. (please see section of 3.2 Evaluation of catalytic activity in the Manuscript)

3) The authors loaded the support with 10 wt% of SnOx. This is a significant loading. Do the authors assume, that even at this high loading, SnOx would remain completely dispersed and not show up on XRD?

Response 3: Thank you very much for pointing out this issue. When the loading capacity of Sn is higher, agglomeration may be caused to a certain extent, while it does not form to a crystal (which may not be detected by XRD), which reduces its catalytic activity. In addition, we have revised the unreasonable statement in the manuscript. (please see section of 3.2 Evaluation of catalytic activity in the Manuscript)

4) If all the materials show excellent dispersion, why does Sn10-KCC show less activity than Sn7-KCC?

Response 4: Thank you very much for pointing out this issue. We have revised the unreasonable statement in the article. (please see section of 3.2 Evaluation of catalytic activity in the Manuscript)

5) The sorption curves for the materials are strange. The MCM-based materials should present a drastically different sorption curve. (https://www.acsmaterial.com/mcm-41.html)

Response 5: Thank you for the reviewer’s insightful comments. The single N₂ adsorption-desorption isotherms curves of Sn₇MCM-41 catalyst materials was provided as blow. However, when it was put together with the curves of other catalysts (shown in Figure 5), and we have stretched out the Figure 5.

N₂ adsorption-desorption isotherms curves of Sn₇MCM-41 catalyst materials.

6) In H₂-TPR curves, if we assume a 7 wt.% loading, and that a similar mass of the sample was measured, the area of the reduction peak should be 7 % of the area for the pure SnO₂. What is the author's explanation for the discrepancy?

Response 6: Thank you for the reviewer’s insightful comments. The Sn species in pure SnO₂ are mainly Sn⁴⁺, while the Sn species in Sn₇@KCC-1 catalyst with 7 wt.% loading are not all in the form of Sn⁴⁺. In addition, the small catalytic dose gap in the test may also cause the gap in peak area. Therefore, its peak area cannot strictly reach 7% of that for SnO₂.

Round 2

Reviewer 1 Report

The authors took some of the feedback into consideration, but did so in a shallow way: how can one talk about low temperature CO oxidation without mentioning any gold catalysts? There are only three references added to small articles (randomly chosen by the authors) about noble metal catalysts, although there are numerous works, including large reviews. None of this has been acknowledged to exist by the authors. Only one article about Co3O4 has been cited (and incorrectly: the reference number 11 has the title: "Reactivity of lattice oxygen 391 in Ti-Site-Substituted SrTiO(3) perovskite catalysts", so it is not about Co3O4), though there are several articles with hundreds of citations.

My second question was answered in a similar fashion: no mention in the text and the reason provided in the response is not shown in any of the presented results by any of the techniques used to characterize the catalysts.

Most of the errors have been removed, but some new minor ones were introduced, e.g., "It, mainly originates" -the comma is an error.

Author Response

1. The authors took some of the feedback into consideration, but did so in a shallow way: how can one talk about low temperature CO oxidation without mentioning any gold catalysts? There are only three references added to small articles (randomly chosen by the authors) about noble metal catalysts, although there are numerous works, including large reviews. None of this has been acknowledged to exist by the authors. Only one article about Co3O4 has been cited (and incorrectly: the reference number 11 has the title: "Reactivity of lattice oxygen 391 in Ti-Site-Substituted SrTiO(3) perovskite catalysts", so it is not about Co3O4), though there are several articles with hundreds of citations.

Response 1: Thank you for the reviewer's insightful comments. We have carefully considered the feedback and have made revisions to the manuscript accordingly. Specifically, we have updated the related references to ensure that the expression is more reasonable and scientifically sound. We appreciate the reviewer's input and believe that these revisions have improved the overall quality of the manuscript.

Reference

6. Xiang, G.H. Zhao, S. Wei, C.D. Liu, C.Y. Fei, H.L. Liu, Z.G. Yin, S.F. Atomically dispersed Au catalysts for preferential oxidation of CO in H₂-rich stream. Appl. Catal. B: Environ. 2021, 296, 120385-120396.
7. Xin, Y. Zhang, N.N. Lv, Y.N. Wang, J. Li, Q. Zhang, Z.L. Room-Temperature CO oxidative coupling for oxamide production over interfacial Au/ZnO catalysts. ACS Catal., 2023, 13, 735−743.
8. Dae, J.M.; Shin, D.; Jeong, H.; Kim, B.S.; Han, J.W.; Lee, H. Highly Water-Resistant La-doped Co₃O₄ Catalyst for CO oxidation, ACS Catal. 2019, 9, 10093−10100.

2. My second question was answered in a similar fashion: no mention in the text and the reason provided in the response is not shown in any of the presented results by any of the techniques used to characterize the catalysts.

Response 2: Thank you for the reviewer’s insightful comments. High content of active components will lead to aggregation, resulting in the covering of the active site, and thus reduce its catalytic activity to CO, which is also shown in some reported catalysts [26, 27]. This is a very common phenomenon in our research field, so we are very sorry to pay too much attention to it, including the design of relevant representation schemes. Your suggestion is very valuable and we will pay closer attention to it in the future study.

Reference

26. Feng, B.; Shi, M.; Liu, J. X.; Han, X. C.; Lan, Z. J.; Gu, H. J.; Wang, X. X.; Sun, H. M.; Zhang, Q. X; Li, H. X.; Y. Wang, Li, H. An efficient defect engineering strategy to enhance catalytic performances of Co₃O₄ nanorods for CO oxidation, J. Hazard. Mater., 2020, 394, 122540.
27. Wang, Y.; Liu, C.; Liao, X.; Liu, Y.; Hou, J.; Pham-Huu, C. Enhancing oxygen activation on high surface area Pd-SnO₂ solid solution with isolated metal site catalysts for catalytic CH₄ combustion, Appl. Surf. Sci. 2021, 564, 150368.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have made a very deep revision of their manuscript (presentation, language and content), which inceased (in my eyes) the quality tremendously. 

Therefore, I recomment the manuscript to be published.

Author Response

Thank you sincerely for your comments on this manuscript.  Your valuable input has significantly improved the quality of our work (the manuscript # Manuscript ID: Catalysts-2457773 entitled “Insights into SnO₂ nanoparticles supported on fibrous meso-porous silica for CO catalytic oxidation”). We greatly appreciate your time and effort in thoroughly reviewing the manuscript and providing insightful feedback. Your suggestions and recommendations have been carefully considered and incorporated, leading to a stronger and more refined manuscript. We are grateful for your contribution and are confident that these improvements will enhance the overall impact and clarity of our research.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors did not answer the questions I presented sufficiently.

There is no section 3.2. The catalytic evaluation section (2.2) was changed minimally. The N₂ sorption results are basically unchanged.  The authors also show a lack of understanding of the methods described and used in their work. According to their answer to my final questions, not all Sn atoms are in the Sn⁴⁺ oxidation state. However, in the DFT model, the authors show only Sn⁴⁺. The same is true for the results of XPS, where only the Sn⁴⁺ oxidation state is observed.

The quality of English was only marginally improved.

Author Response

1. There is no section 3.2. The catalytic evaluation section (2.2) was changed minimally. The N₂ sorption results are basically unchanged. The authors also show a lack of understanding of the methods described and used in their work. According to their answer to my final questions, not all Sn atoms are in the Sn⁴⁺ oxidation state. However, in the DFT model, the authors show only Sn⁴⁺. The same is true for the results of XPS, where only the Sn⁴⁺ oxidation state is observed.

 

Response 1: Thank you for the reviewer’s insightful comments. We have made theoretical adjustments to the chapter order of the manuscript based on the editor’s feedback. We moved more detailed evaluation information of “4.2. Evaluation of the catalytic performance” from the Supplementary Materials to the Manuscript. Sorry for our last rude reply, as you have rightly pointed out, nearly all of the tin (Sn) present in the catalyst exists in the form of Sn⁴⁺. Furthermore, we have retested the H₂-TPR (Hydrogen Temperature Programmed Reduction) curve of the Sn₇@KCC-1 catalyst and the obtained results are now presented in Figure S3. Upon comparison with the previous test, we observed a significant enhancement in the reduction peak area of Sn⁴⁺, which now closely resembles approximately 7% of the area exhibited by the SnO₂ catalyst.

These adjustments aim to strengthen the overall presentation and comprehensibility of our findings. We are grateful for the reviewer’s and editor’s valuable input, which has undoubtedly contributed to the enhancement of the manuscript. (Please see attached file)

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

The authors still failed to clarify the results of BET. The number values do not correlate with the presented isotherms. The isotherm for the MCM-41 material exhibits no jump in the region associated with microporosity.

The English of the manuscript has been improved to the point where negligible corrections are necessary.