Theoretical Investigation on the Catalytic Effect and Mechanism of Pure and Cu−Doped SBA−15 Molecular Sieves on the Decomposition of Dimethyl Sulfoxide

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This review report has been removed from the review record as it did not meet MDPI’s review report standards (https://www.mdpi.com/reviewers#_bookmark11).

Reviewer 2 Report

Comments and Suggestions for Authors

I found your submitted work interesting and worth recommending for publication. 

Author Response

The reviewer found the manuscript  interesting and worth recommending for publication without providing any specific revision suggestions. Therefore, there was no response to the reviewer's comments.

Reviewer 3 Report

Comments and Suggestions for Authors

This work is worthwhile to be publish in this journal after minor revision. The following issues should be addressed:

1. Introduction is well-organized but the importance and novelty of the research should be highlighted and more clearly stated. The authors should give some examples of works in the bibliography, to clear the advantage of their work in comparison with those works.

2. The manuscript contains some minor typo/grammar errors, please check all of it.

3. Introduction part, if possible, some important and relative reports silica that could help:

Delta University Scientific Journal Vol.05-Iss.02 (2022) 321-339

https://doi.org/10.1016/j.jmrt.2022.03.067

https://doi.org/10.1016/j.colsurfa.2021.126361

https://doi.org/10.1007/s10971-022-05755-7

4. Abstract not targeted; the authors should rephrase it.

Hence, I recommend it accepted for publication after minor revisions.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

1

Abstract should contain more relevant research results, and link to the conclusion.

Conclusion should be improved, giving some more details of the research.

2

It seams that in some phrases, the author may want to use e.g. instead of i.e.

The abbreviation "e.g." stands for exempli gratia and means “for example.” 

The abbreviation "i.e." stands for id est and means “that is.”

3

Figure 5 and 6, to be adequated within the margin limits.

DFT should be explained.

4

Where the data come from? Please detail.

Where exactly was the experiments/tests carried out? Please detail.

How by means of which equipment/resources could the authors propose components strcuture adjustments? Details...

The graphs/figures, are being extracted from which tool?

5

I do not really understand this, and I would suggest the authors to rephrase.

"The transformation of oil shale into liquid shale oil"

Low by how much? Would be very interesting to add some quantitative values.

"the pyrolysis conversion rate of oil shale is relatively low"

6

I would be very carefull with such sentence. With technologies and developments, new reserves are being found, the recovery factor is being increased.

"As a result, the traditional energy reserves have proven inadequate to keep up with the swift pace of energy consumption brought forth by human development. "

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 5 Report (New Reviewer)

Comments and Suggestions for Authors

The manuscript presents a well-structured DFT study investigating Cu-doped SBA-15’s catalytic role in DMSO decomposition, a model for organic sulfur cracking in oil shale. While the computational methodology is robust and conclusions are supported by data, several aspects require clarification to ensure reproducibility and contextualize practical implications. Minor revisions are recommended before final validation.

1. DMSO is a valid model for sulfoxides, but oil shale kerogen contains diverse heteroatoms (e.g., N, complex S-species). The study does not discuss how competitive adsorption or co-existing molecules might affect catalysis. I suggest adding a paragraph in the Introductionor Discussion acknowledging limitations of the DMSO model and plans for future studies (e.g., larger kerogen fragments).
2. The hydroxylated amorphous SiO₂ surface (Figure 1) is reasonable but lacks validation against experimental SBA-15 structures (e.g., pore size effects, Cu distribution). I suggest citing experimental studies confirming Cu incorporation in SBA-15’s mesopores (e.g., XRD/EXAFS data in References 12–13) to strengthen model credibility.
3. While charge transfer (Cu → O₆) is noted (Table 1), the origin of Cu’s catalytic activity (e.g., Lewis acidity, redox properties) remains underexplored. Include electron localization function (ELF) or charge density difference plots to visualize Cu–S/O interactions.
4. Clarify why C–H dissociation (ΔE = 39.8 kcal/mol) is "competitive" despite higher barriers than C–S cleavage (31.1 kcal/mol).
5. Adsorption energies of DMSO on pure (32.6 kcal/mol) and Cu-doped SBA-15 (32.6 kcal/mol) are identical (Sections 3.2.1–3.2.2, Figures 2–3). The authors fail to reconcile this equivalence with Cu-doped SBA-15’s significantly enhanced catalytic activity(C–S barrier reduced by ~40 kcal/mol). If adsorption strength is similar, why does doping drastically alter reactivity? No discussion of adsorption mode differences (H-bonding vs. S–Cu interaction) and their implications for bond activation, and no electronic analysis (e.g., charge transfer during adsorption) to explain how Cu facilitates bond cleavage despite similar adsorption energy. Please improve the above two questions if possible.
6. Table 1 shows Cu doping elongates Cu–Obb​bonds (1.62–1.64 Å → 1.80–1.83 Å) and reduces Obb​ charge (e.g., –0.884 → –0.665 |e|). The authors state these changes "provide additional space for adsorption" but neglect their catalytic role. How do elongated Cu–O bonds and electron-deficient Obb​ atoms promote methyl binding (Cu-DS4, ΔG = –16.4 kcal/mol)? Does charge redistribution enhance Lewis acidity of Cu sites? PDOS (Figure 4) confirms S–Cu interaction but lacks linkage to reactivity.
7. Cu doping reduces C–S cleavage barrier from ~75 kcal/mol (pure) to 31.1 kcal/mol (doped). The ~40 kcal/mol reduction is highlighted but not mechanistically explained. Does it stem from transition-state stabilization or reactant destabilization?
8. Methyl binds preferentially to Obb​over hydroxyl O in Cu-DS4 (Figure 6, Table 2). No exploration of why Obb​ is favored. Is it due to sterics, electronics, or the electron-deficient nature of Obb​ post-Cu doping (Table 1)?