Progress in the Synthesis and Applications of C₃N₅-Based Catalysts in the Piezoelectric Catalytic Degradation of Organics

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The work entitled “Progress in the Synthesis and Applications of C₃N₅-based Catalysts in Piezoelectric-Catalyzed Degradation of Organics” is interesting. The study extensively reviews C₃N₅-based catalysts used in piezoelectric catalysis, specifically for degrading organic pollutants in water, and emphasizes the potential of C₃N₅-based catalysts for eco-friendly degradation processes. However, the author needs to make some significant improvements in the manuscript.

Comments

1. The paper mentions wastewater treatment but doesn’t research deeply into practical implications or real-world case studies. Discussing how these catalysts have been applied or tested in field scenarios would enhance their practical relevance.
2. The abstract should include some quantitative results obtained from the work.

3.     The paper primarily discusses piezoelectric catalysis but lacks a comprehensive comparison with other catalytic methods such as photocatalysis or electrocatalysis, suggesting a need for a more balanced analysis.

4.     The authors note that less research has been conducted on air purification applications but fail to explore this direction further. Given the increasing concern about air quality, more emphasis on how C₃N₅ could address air pollutants would improve the paper's relevance.

5.     The paper lacks comparative performance data for C₃N₅-based catalysts, making it challenging to evaluate their practical advantages. A detailed comparative analysis is recommended.

6.     The future research suggestions lack insight into challenges and opportunities. It should offer specific suggestions for future research, such as exploring alternative synthesis techniques.

7. Review the paper for its typological and grammatical mistakes i.e. (Start of the abstract).
8. Review the caption of figures 4, 5 and 6.

Author Response

1. The paper mentions wastewater treatment but doesn’t research deeply into practical implications or real-world case studies. Discussing how these catalysts have been applied or tested in field scenarios would enhance their practical relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that the discussion on wastewater treatment in the paper lacks in-depth practical impact analysis and real case studies. Therefore, we plan to add a discussion on the application examples and effects of C₃N₅ based catalysts in actual wastewater treatment scenarios in the revised version. Thank you for your suggestions on improving the quality of our paper.

Line 178-193: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

2. The abstract should include some quantitative results obtained from the work.

Reponse: Thank you to the reviewer for reviewing and providing feedback on our paper. We recognize that the abstract lacks specific quantitative results, which may affect readers' understanding of the research contribution. In the revised version, we have made modifications to the abstract section

Line 7-19: Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

3. The paper primarily discusses piezoelectric catalysis but lacks a comprehensive comparison with other catalytic methods such as photocatalysis or electrocatalysis, suggesting a need for a more balanced analysis.

Reponse: Thank you to the reviewer for their detailed review and constructive comments on our paper. We recognize that although this article mainly focuses on piezoelectric catalysis, it lacks comparison with other catalytic methods such as photocatalysis and electrocatalysis. In order to enhance the comprehensiveness and depth of the article, we have added the following content in the revised version:

Line 179-196: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C3N5, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects. Fu et al. successed synthesized dual defect C3N5 materials with O doping and N vacancies through thermal polymerization coupled with thermal etching method. ³.

4. The authors note that less research has been conducted on air purification applications but fail to explore this direction further. Given the increasing concern about air quality, more emphasis on how C₃N₅ could address air pollutants would improve the paper's relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that there is relatively little research on air purification applications. However, as people's attention to air quality increases, we will further explore the potential of C₃N₅ in removing air pollutants. In the revised manuscript, we plan to add relevant literature reviews to emphasize the application value of C₃N₅ and explore its specific mechanisms and advantages in the field of air purification. We believe that this will significantly enhance the relevance and contribution of the paper.

Line 365-370: Photocatalytic technology can be used to purify volatile organic compounds in the air. This is because these small molecules can react with photo-generated electrons/holes with redox ability. The original C₃N₅ has been proven to be an excellent candidate for the adsorption of some small molecules due to its high nitrogen content as an active center. Therefore, it is necessary and meaningful to study how to apply C₃N₅ photocatalytic technology in air pollution control.

5. The paper lacks comparative performance data for C₃N₅-based catalysts, making it challenging to evaluate their practical advantages. A detailed comparative analysis is recommended.

Reponse: Thank you for your suggestions. We recognize that the lack of comparative performance data for C₃N₅ based catalysts in the current manuscript does indeed affect the evaluation of their actual advantages. In the revised manuscript, we will add a detailed comparative analysis of C₃N₅ with other known catalysts. Thank you for your valuable feedback. We will strive to enhance the depth and rigor of our paper.

Line 179-188: Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

6. The future research suggestions lack insight into challenges and opportunities. It should offer specific suggestions for future research, such as exploring alternative synthesis techniques.

Reponse: Thank you for your feedback. We will strengthen the elaboration of future research recommendations and specifically discuss the challenges and opportunities of C₃N₅ in the synthesis process. In the revised manuscript, we will propose specific suggestions for exploring alternative synthesis techniques, such as green synthesis methods and efficient reaction conditions, to enhance the performance of C₃N₅. In addition, its potential in different application fields will be explored to provide direction for future research. Thank you for your guidance. We will strive to make the suggestions more specific and practical.

Line 380-390: In the future, we will explore more sustainable synthesis methods, such as using green chemistry techniques or novel catalysts, to improve synthesis efficiency and reduce environmental impact. Identifying and overcoming potential technical challenges in the synthesis process, such as optimizing reaction conditions, improving yield, and controlling material purity, are important steps in driving research. Thoroughly explore the application of C₃N₅ in fields such as environmental protection, energy conversion, and materials science, design specific experimental and research questions, and verify its actual effectiveness. Encourage interdisciplinary collaboration and promote in-depth research and widespread application of C₃N₅ by combining knowledge from fields such as chemistry, materials science, and engineering.

7. Review the paper for its typological and grammatical mistakes i.e. (Start of the abstract).

Reponse: Thank you so much for your thoughtful feedback on the paper. I truly appreciate your insights and will carefully review the abstract to identify and correct any typographical and grammatical errors. My goal is to enhance the clarity and coherence of the sentences while ensuring consistent terminology and formatting. Your guidance is invaluable, and I will implement these changes promptly to improve the overall quality of the paper. The specific changes are as follows:

Line 7-19:Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

8. Review the caption of figures 4, 5 and 6.

Reponse: Thank you for the reviewer's attention to the titles of Figures 4, 5, and 6. We will carefully review the titles of these charts and ensure that they more clearly reflect the content of the charts and their relevance to the research. In the revised version, we will make necessary modifications based on the suggestions of the reviewers to improve the readability of the charts and the accuracy of information communication. Thank you again for your careful review of our work.

Line 380-390: Figure 4. The influences degradation, including: (a) SPC concentration, (b) U-C₃N₅ dosage, (c) initial pH of SMZ solution, (d) anions, and fulvic acid., (b) and (d) SPC concentration and U-C₃N₅ dosage. Test bar Piece :CMZ, initial 10mgL-1, T= 250.5 °C, visible light ⁴.

Line 320-321: Figure 5. Co-C₃N₅ activates PMS for PCB28 degradation: (a) degrade kinetics, (b) The catalytic ability of Co-C₃N₅ to PCB28 after four cycles[17].

Line 347-349: Figure 6. The effects of Co CsNs loading (a) PMS concentration, (b) and initial reaction pH, (c) on the degradation of PCB28 by Co CsNs/PMS. Reaction Conditions: [Co CsNs = 1.0g L^-1, [PCB28]=0.5 mg L^-1, [PMS] = 0.5-3.0 mM, pH = 3.0-1.0 (buffer solution) [17].

Reviewer 2 Report

Comments and Suggestions for Authors

Yin et. al. reported the manuscript which consists of C₃N₅ based material, showing degradation of organics. The material acts as piezoelectric catalyst. Flow of presentation is fine. However there is major scientific flaws. Thus I believe that major revision is necessary before taking any decision . Some of the flaws are mentioned below for authors' guidance.

 

1) There is no experimental section in this manuscript. Thus reproduction the result and future application, it is very difficult. Therefore authors should write synthesis details and experimental set up in details for each of the study.

2) Authors have mentioned that they have done AIMD calculation for confirming the stability. However there is no supporting data for this calculation.

3) To confirm the formation of C3N5 material, authors should do other spectroscopic characterizations such as NMR,PXRD, FTIR etc. and match with their claim.

4) Authors should give comparison table to compare catalytic efficiency of their material in each condition with other reported compounds.

5) Authors should give plausible mechanism to show how the reported material is acting piezoelectric catalyst for degradation of Rhodamine B.

6) To check the recyclability of the material, authors should study PXRD and FTIR after each cycle, to examine the status of the material.

Author Response

1) There is no experimental section in this manuscript. Thus reproduction the result and future application, it is very difficult. Therefore authors should write synthesis details and experimental set up in details for each of the study.

Reponse: Thank you to the reviewer for their careful review and feedback on our manuscript. We understand that there are indeed difficulties in replicating results and future applications without an experimental section. Therefore, in the revised version, we have cited the literature mentioned in each study, which reports the synthesis details and experimental settings of the materials. Thank you again for your suggestions. We will strive to improve the quality of the paper.

2) Authors have mentioned that they have done AIMD calculation for confirming the stability. However there is no supporting data for this calculation.

Reponse: Thank you to the reviewer for their careful review and feedback on our manuscript. We recognize that the lack of supporting data in AIMD calculations can indeed affect the persuasiveness of the results. In the revised version, we will supplement relevant supporting data, including the detailed process of AIMD calculation. We greatly appreciate your suggestions and will strive to improve the quality of the paper.

Line 347-349: First principles calculations are performed using the Vienna ab initio simulation package (VASP) based on density functional theory (DFT). The electron ion interaction is described by the Projection Enhanced Wave (PAW) potential, using the Perdew Burke Ernzerhof (PBE) form of Generalized Gradient Approximation (GGA) as the exchange correlation functional, and introducing the DFT-D3 functional to consider van der Waals interactions, in order to effectively reproduce the lattice constants in the experiment. HSE06 hybrid functionals are used to provide more reliable electronic band structures and light absorption properties. The Kohn Sham electron wave function is developed using a 520 eV plane wave, with energy convergence set at 10^-5 eV and residual force of 0.01 eV Å ⁻¹. The Brillouin zone integration uses a 7 × 7 × 1 k-point grid. To eliminate the interaction between adjacent images, a vacuum space of over 20 Å was applied in the z-direction. The electrocatalytic reaction calculation uses 2 × 2 super units. The formula for calculating the formation energy of C₃N₅ monolayer is Ef=E (C₃N₅) − (m μ C+n μ N), where E (C₃N₅) is the total energy of the monolayer, m and n are the number of carbon and nitrogen atoms per unit cell, and μC and μN are obtained from graphene and N₂, respectively. The photon spectrum is calculated through the Phonopy code and VASP interface, and first principles molecular dynamics simulations are conducted under the gauge ensemble (NVT) with a time step of 1.0 fs ⁵.

3) To confirm the formation of C₃N₅ material, authors should do other spectroscopic characterizations such as NMR, PXRD, FTIR etc. and match with their claim.

Reponse: Thank you so much for your kind suggestion. We truly appreciate your recognition of the significance of additional spectroscopic techniques like NMR, PXRD, and FTIR in confirming the characterization of materials. These methods indeed provide great insights. However, we would like to gently clarify that our paper is a review article that mainly focuses on summarizing and analyzing the existing research rather than presenting new experimental data. As a result, we are not able to carry out these additional characterizations by ourselves. We hope this explanation brings some understanding, and we are really grateful for your understanding and continuous support. Thank you once again for your precious comment!

4) Authors should give comparison table to compare catalytic efficiency of their material in each condition with other reported compounds.

Response: Thank you for your review. Your suggestion is of great significance to the improvement of the quality of our manuscript. This is a review article and we have not synthesized the relevant catalysts ourselves. By reviewing the relevant literature, we collected some relevant literature on the degradation of pollutants by C₃N₅ based piezoelectric catalysts. Specifically as follows：

Catalytic system	Reaction conditions	Target pollutants	Removal efficiency	Ref
RN-g-C3N5	0.02 g RN-g-C3N5 20 Ml 20 mg/L MB	Methylene Blue (MB)	98%(120 min)	6
AgCl/g-C3N5	50 mg AgCl/g-C3N5 50 mL 10 mg/L RhB	Rhodamine B (RhB)	96 % (30 min)	7
CeTiO6/g-C3N5	1.6 g/L CeTi2O6/g-C3N575 mL 10 ppm 2.4-DCP300 W xenon lamp (λ > 420 nm)	2, 4-dichlorophenol (2,4-DCP)	96 % (120 min)	8
CdS/ g-C3N5	0.1 g/L CdS-MHP50 mL 0.01 mM RhB1 sun AM1.5 G	Rhodamine B (RhB)	90 % (80 min)	9
Xp-/g-C3N5	1 sun AM1.5 g 6P-gC3N55 ppm RhB, 20 ppm TC350 W xenon lamp	Rhodamine B (RhB)Tetracycline (TC)	100 % (180 min)	10
Ag3PO4/g-C3N5	1.0 g/L Ag3PO4/C3N550 mL 20 mg/L TCH300 W Xe lamp (λ > 400 nm)	Tetracycline hydrochloride (TCH)	90.5 % (60 min)	11
FeOCl/ g-C3N5	1.0 mg/mL Catalyst75 mL 10 mg/L TC30 % 200 μL H2O2	Tetracycline (TC)	95 % (40 min)	12
CDs/MoS2/g-C3N5	0.02 g/L Catalyst 50 mL 30 mg/L MB300 W Xe lamp (λ > 420 nm)	Methylene blue (MB)	94 % (120 min)	13

 

5) Authors should give plausible mechanism to show how the reported material is acting piezoelectric catalyst for degradation of Rhodamine B.

Reponse: We appreciate the reviewer’s valuable suggestion regarding the need for a plausible mechanism to explain how the reported material acts as a piezoelectric catalyst for the degradation of Rhodamine B. In our revised manuscript, we will include a detailed discussion of the proposed mechanism. By providing this mechanistic insight, we aim to strengthen our argument and clarify the role of the piezoelectric properties in the catalytic process. Thank you for your constructive feedback, which will help improve the quality of our work.

Line 64-66: The principle of ZIF-8 nanoparticles degrading Rhodamine B may be through adsorp-tion and the generation of active substances to react with it and other mechanisms to achieve.

Line 223-237: The principle of the electrocatalytic system effectively interacting with Rhodamine B with the assistance of ultrasound is that ultrasound can promote mass transfer and reaction kinetics, and can also cause physical and chemical effects on the reaction sys-tem, such as generating cavitation bubbles that can enhance the contact and reaction between the electrocatalyst and RhB.

6) To check the recyclability of the material, authors should study PXRD and FTIR after each cycle, to examine the status of the material.

Reponse: Thank you for your comments. Your comments are very helpful to improve the quality of the manuscript. So sorry, we only found the SEM images after the relevant recycling, and we could clearly see the cracks on the surface of C3N5 after the reaction.

 

The SEM of C₃N₅ reaction diagram after the cycle

1. Wang, T.; Song, N.;  Yao, S.;  Wang, Y.;  Wang, Q.; Yu, H., Oxygen-doped defects modified C3N5 in enhanced molecule oxygen photoactivation for tetracycline hydrochloride degradation and H2O2 in situ production: Double pathways of 1O2 and O2–· high yield. Chemical Engineering Journal 2024.
2. Xiang, L.; Haijuan, Z.;  Wei, X.;  Jiantong, W.;  Gang, W.;  Qi, G.;  Heping, L.;  Lijuan, L.; Wanyi, L., Effective strategy for C3N5 with improved photodegradation performance: the key role of the robust built-in electric field and enhanced oxygen adsorption capacity. Journal of Environmental Chemical Engineering 2024.
3. Fu, C.; Wu, T.;  Sun, G.;  Yin, G.;  Wang, C.;  Ran, G.; Song, Q., Dual-defect enhanced piezocatalytic performance of C3N5 for multifunctional applications. Applied Catalysis B: Environmental 2023, 323.
4. Ma, C.; Yu, Z.;  Wei, J.;  Tan, C.;  Yang, X.;  Wang, T.;  Yu, G.;  Zhang, C.; Li, X., Metal-free ultrathin C3N5 photocatalyst coupling sodium percarbonate for efficient sulfamethoxazole degradation. Applied Catalysis B: Environmental 2022, 319.
5. Qi, S.; Fan, Y.;  Wang, J.;  Song, X.;  Li, W.; Zhao, M., Metal-free highly efficient photocatalysts for overall water splitting: C3N5 multilayers. Nanoscale 2020, 12 (1), 306-315.
6. Wang, H.; Li, M.;  Lu, Q.;  Cen, Y.;  Zhang, Y.; Yao, S., A Mesoporous Rod-like g-C3N5 Synthesized by Salt-Guided Strategy: As a Superior Photocatalyst for Degradation of Organic Pollutant. ACS Sustainable Chemistry & Engineering 2018, 7 (1), 625-631.
7. Vadivel, S.; Hariganesh, S.;  Paul, B.;  Rajendran, S.;  Habibi-Yangjeh, A.;  Maruthamani, D.; Kumaravel, M., Synthesis of novel AgCl loaded g-C3N5 with ultrahigh activity as visible light photocatalyst for pollutants degradation. Chemical Physics Letters 2020, 738.
8. Vadivel, S.; Hariganesh, S.;  Paul, B.;  Mamba, G.; Puviarasu, P., Highly active novel CeTi2O6/g-C3N5 photocatalyst with extended spectral response towards removal of endocrine disruptor 2, 4-dichlorophenol in aqueous medium. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2020, 592.
9. Alam, K. M.; Jensen, C. E.;  Kumar, P.;  Hooper, R. W.;  Bernard, G. M.;  Patidar, A.;  Manuel, A. P.;  Amer, N.;  Palmgren, A.;  Purschke, D. N.;  Chaulagain, N.;  Garcia, J.;  Kirwin, P. S.;  Shoute, L. C. T.;  Cui, K.;  Gusarov, S.;  Kobryn, A. E.;  Michaelis, V. K.;  Hegmann, F. A.; Shankar, K., Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires. ACS Applied Materials & Interfaces 2021, 13 (40), 47418-47439.
10. Hu, C.; Lin, Y.-H.;  Yoshida, M.; Ashimura, S., Influence of Phosphorus Doping on Triazole-Based g-C3N5 Nanosheets for Enhanced Photoelectrochemical and Photocatalytic Performance. ACS Applied Materials & Interfaces 2021, 13 (21), 24907-24915.
11. Yin, H.; Cao, Y.;  Fan, T.;  Zhang, M.;  Yao, J.;  Li, P.;  Chen, S.; Liu, X., In situ synthesis of Ag3PO4/C3N5 Z-scheme heterojunctions with enhanced visible-light-responsive photocatalytic performance for antibiotics removal. Science of The Total Environment 2021, 754.
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Reviewer 3 Report

Comments and Suggestions for Authors

Wang, Meng and coworkers have presented an interesting review on synthesis and applications of C₃N₅-based catalysts in piezoelectric-catalysed degradation of organics. The manuscript is well-written, and the figures are effectively presented. In this reviewer’s opinion, the manuscript is ready for publication in Catalysts.

Author Response

1. The paper mentions wastewater treatment but doesn’t research deeply into practical implications or real-world case studies. Discussing how these catalysts have been applied or tested in field scenarios would enhance their practical relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that the discussion on wastewater treatment in the paper lacks in-depth practical impact analysis and real case studies. Therefore, we plan to add a discussion on the application examples and effects of C₃N₅ based catalysts in actual wastewater treatment scenarios in the revised version. Thank you for your suggestions on improving the quality of our paper.

Line 178-193: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

2. The abstract should include some quantitative results obtained from the work.

Reponse: Thank you to the reviewer for reviewing and providing feedback on our paper. We recognize that the abstract lacks specific quantitative results, which may affect readers' understanding of the research contribution. In the revised version, we have made modifications to the abstract section

Line 7-19: Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

3. The paper primarily discusses piezoelectric catalysis but lacks a comprehensive comparison with other catalytic methods such as photocatalysis or electrocatalysis, suggesting a need for a more balanced analysis.

Reponse: Thank you to the reviewer for their detailed review and constructive comments on our paper. We recognize that although this article mainly focuses on piezoelectric catalysis, it lacks comparison with other catalytic methods such as photocatalysis and electrocatalysis. In order to enhance the comprehensiveness and depth of the article, we have added the following content in the revised version:

Line 179-196: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C3N5, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects. Fu et al. successed synthesized dual defect C3N5 materials with O doping and N vacancies through thermal polymerization coupled with thermal etching method. ³.

4. The authors note that less research has been conducted on air purification applications but fail to explore this direction further. Given the increasing concern about air quality, more emphasis on how C₃N₅ could address air pollutants would improve the paper's relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that there is relatively little research on air purification applications. However, as people's attention to air quality increases, we will further explore the potential of C₃N₅ in removing air pollutants. In the revised manuscript, we plan to add relevant literature reviews to emphasize the application value of C₃N₅ and explore its specific mechanisms and advantages in the field of air purification. We believe that this will significantly enhance the relevance and contribution of the paper.

Line 365-370: Photocatalytic technology can be used to purify volatile organic compounds in the air. This is because these small molecules can react with photo-generated electrons/holes with redox ability. The original C₃N₅ has been proven to be an excellent candidate for the adsorption of some small molecules due to its high nitrogen content as an active center. Therefore, it is necessary and meaningful to study how to apply C₃N₅ photocatalytic technology in air pollution control.

5. The paper lacks comparative performance data for C₃N₅-based catalysts, making it challenging to evaluate their practical advantages. A detailed comparative analysis is recommended.

Reponse: Thank you for your suggestions. We recognize that the lack of comparative performance data for C₃N₅ based catalysts in the current manuscript does indeed affect the evaluation of their actual advantages. In the revised manuscript, we will add a detailed comparative analysis of C₃N₅ with other known catalysts. Thank you for your valuable feedback. We will strive to enhance the depth and rigor of our paper.

Line 179-188: Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

6. The future research suggestions lack insight into challenges and opportunities. It should offer specific suggestions for future research, such as exploring alternative synthesis techniques.

Reponse: Thank you for your feedback. We will strengthen the elaboration of future research recommendations and specifically discuss the challenges and opportunities of C₃N₅ in the synthesis process. In the revised manuscript, we will propose specific suggestions for exploring alternative synthesis techniques, such as green synthesis methods and efficient reaction conditions, to enhance the performance of C₃N₅. In addition, its potential in different application fields will be explored to provide direction for future research. Thank you for your guidance. We will strive to make the suggestions more specific and practical.

Line 380-390: In the future, we will explore more sustainable synthesis methods, such as using green chemistry techniques or novel catalysts, to improve synthesis efficiency and reduce environmental impact. Identifying and overcoming potential technical challenges in the synthesis process, such as optimizing reaction conditions, improving yield, and controlling material purity, are important steps in driving research. Thoroughly explore the application of C₃N₅ in fields such as environmental protection, energy conversion, and materials science, design specific experimental and research questions, and verify its actual effectiveness. Encourage interdisciplinary collaboration and promote in-depth research and widespread application of C₃N₅ by combining knowledge from fields such as chemistry, materials science, and engineering.

7. Review the paper for its typological and grammatical mistakes i.e. (Start of the abstract).

Reponse: Thank you so much for your thoughtful feedback on the paper. I truly appreciate your insights and will carefully review the abstract to identify and correct any typographical and grammatical errors. My goal is to enhance the clarity and coherence of the sentences while ensuring consistent terminology and formatting. Your guidance is invaluable, and I will implement these changes promptly to improve the overall quality of the paper. The specific changes are as follows:

Line 7-19:Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

8. Review the caption of figures 4, 5 and 6.

Reponse: Thank you for the reviewer's attention to the titles of Figures 4, 5, and 6. We will carefully review the titles of these charts and ensure that they more clearly reflect the content of the charts and their relevance to the research. In the revised version, we will make necessary modifications based on the suggestions of the reviewers to improve the readability of the charts and the accuracy of information communication. Thank you again for your careful review of our work.

Line 380-390: Figure 4. The influences degradation, including: (a) SPC concentration, (b) U-C₃N₅ dosage, (c) initial pH of SMZ solution, (d) anions, and fulvic acid., (b) and (d) SPC concentration and U-C₃N₅ dosage. Test bar Piece :CMZ, initial 10mgL-1, T= 250.5 °C, visible light ⁴.

Line 320-321: Figure 5. Co-C₃N₅ activates PMS for PCB28 degradation: (a) degrade kinetics, (b) The catalytic ability of Co-C₃N₅ to PCB28 after four cycles[17].

Line 347-349: Figure 6. The effects of Co CsNs loading (a) PMS concentration, (b) and initial reaction pH, (c) on the degradation of PCB28 by Co CsNs/PMS. Reaction Conditions: [Co CsNs = 1.0g L^-1, [PCB28]=0.5 mg L^-1, [PMS] = 0.5-3.0 mM, pH = 3.0-1.0 (buffer solution) [17].

Reviewer 4 Report

Comments and Suggestions for Authors

The review paper of Wang, Meng et al. describes recent developments in the synthesis of carbon nitride based piesoelectric catalysts for degradation of water pollutants.

Being non-specialist in this particular field, I have read the paper with interest learning some new things and ideas.

However, I am not entirely with authors in their approach to writing a review. It looks much more as a simple compilation of several (3 or 4) research papers and is overloaded with technical details lacking generalization and perspective.

In particular, I would like to know more about different methods of waste removal, other methods being under development, their relative costs, advantages and disadvantages. These improvements could make really a review from this material.

I suggest reconsideration after major revision. 

Comments on the Quality of English Language

In general English is OK and easily readable.

However please check the structure of sentences in lines 180-183, 211, 219, 231, 247

Author Response

The work entitled “Progress in the Synthesis and Applications of C3N5-based Catalysts in Piezoelectric-Catalyzed Degradation of Organics” is interesting. The study extensively reviews C3N5-based catalysts used in piezoelectric catalysis, specifically for degrading organic pollutants in water, and emphasizes the potential of C3N5-based catalysts for eco-friendly degradation processes. However, the author needs to make some significant improvements in the manuscript.

1. The paper mentions wastewater treatment but doesn’t research deeply into practical implications or real-world case studies. Discussing how these catalysts have been applied or tested in field scenarios would enhance their practical relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that the discussion on wastewater treatment in the paper lacks in-depth practical impact analysis and real case studies. Therefore, we plan to add a discussion on the application examples and effects of C₃N₅ based catalysts in actual wastewater treatment scenarios in the revised version. Thank you for your suggestions on improving the quality of our paper.

Line 178-193: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

2. The abstract should include some quantitative results obtained from the work.

Reponse: Thank you to the reviewer for reviewing and providing feedback on our paper. We recognize that the abstract lacks specific quantitative results, which may affect readers' understanding of the research contribution. In the revised version, we have made modifications to the abstract section

Line 7-19: Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

3. The paper primarily discusses piezoelectric catalysis but lacks a comprehensive comparison with other catalytic methods such as photocatalysis or electrocatalysis, suggesting a need for a more balanced analysis.

Reponse: Thank you to the reviewer for their detailed review and constructive comments on our paper. We recognize that although this article mainly focuses on piezoelectric catalysis, it lacks comparison with other catalytic methods such as photocatalysis and electrocatalysis. In order to enhance the comprehensiveness and depth of the article, we have added the following content in the revised version:

Line 179-196: Liu et al. ¹ synthesized porous C₃N₅ (p-C₃N₅) to activate periodate (PI) for degradation of tetracycline (TC) under visible light conditions. The experimental results confirm that the porous structure of C₃N₅ generates abundant defects as active sites, which not only improves the efficiency of photoelectric and electron hole separation, but also promotes PI activation and the generation of reactive oxygen species, achieving a significant improvement in PI assisted photocatalytic performance. Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C3N5, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects. Fu et al. successed synthesized dual defect C3N5 materials with O doping and N vacancies through thermal polymerization coupled with thermal etching method. ³.

4. The authors note that less research has been conducted on air purification applications but fail to explore this direction further. Given the increasing concern about air quality, more emphasis on how C₃N₅ could address air pollutants would improve the paper's relevance.

Reponse: Thank you for the valuable comments provided by the reviewer. We recognize that there is relatively little research on air purification applications. However, as people's attention to air quality increases, we will further explore the potential of C₃N₅ in removing air pollutants. In the revised manuscript, we plan to add relevant literature reviews to emphasize the application value of C₃N₅ and explore its specific mechanisms and advantages in the field of air purification. We believe that this will significantly enhance the relevance and contribution of the paper.

Line 365-370: Photocatalytic technology can be used to purify volatile organic compounds in the air. This is because these small molecules can react with photo-generated electrons/holes with redox ability. The original C₃N₅ has been proven to be an excellent candidate for the adsorption of some small molecules due to its high nitrogen content as an active center. Therefore, it is necessary and meaningful to study how to apply C₃N₅ photocatalytic technology in air pollution control.

5. The paper lacks comparative performance data for C₃N₅-based catalysts, making it challenging to evaluate their practical advantages. A detailed comparative analysis is recommended.

Reponse: Thank you for your suggestions. We recognize that the lack of comparative performance data for C₃N₅ based catalysts in the current manuscript does indeed affect the evaluation of their actual advantages. In the revised manuscript, we will add a detailed comparative analysis of C₃N₅ with other known catalysts. Thank you for your valuable feedback. We will strive to enhance the depth and rigor of our paper.

Line 179-188: Li et al. ² constructed a built-in electric field (BIEF) that facilitates the transport and separation of photo generated carriers in C₃N₅, effectively enhancing its photocatalytic performance. The powerful BIEF and enhanced oxygen adsorption capacity synergistically promote the removal efficiency of levofloxacin hydrochloride (LFH) by KACN-2 (0.0299min^-1) under visible light, which is 3.8 times higher than that of CN (0.0086min^-1). Wang et al. ¹ synthesized a novel C₃N₅ with multiple oxygen doped defect sites using a feasible one-step calcination method. The research results demonstrate the universality and feasibility of using O-C₃N₅ photoactivation molecular oxygen for deep treatment of complex wastewater, and provide a comprehensive understanding of the enhancement of C₃N₅ molecular oxygen photoactivation by O doping defects.

6. The future research suggestions lack insight into challenges and opportunities. It should offer specific suggestions for future research, such as exploring alternative synthesis techniques.

Reponse: Thank you for your feedback. We will strengthen the elaboration of future research recommendations and specifically discuss the challenges and opportunities of C₃N₅ in the synthesis process. In the revised manuscript, we will propose specific suggestions for exploring alternative synthesis techniques, such as green synthesis methods and efficient reaction conditions, to enhance the performance of C₃N₅. In addition, its potential in different application fields will be explored to provide direction for future research. Thank you for your guidance. We will strive to make the suggestions more specific and practical.

Line 380-390: In the future, we will explore more sustainable synthesis methods, such as using green chemistry techniques or novel catalysts, to improve synthesis efficiency and reduce environmental impact. Identifying and overcoming potential technical challenges in the synthesis process, such as optimizing reaction conditions, improving yield, and controlling material purity, are important steps in driving research. Thoroughly explore the application of C₃N₅ in fields such as environmental protection, energy conversion, and materials science, design specific experimental and research questions, and verify its actual effectiveness. Encourage interdisciplinary collaboration and promote in-depth research and widespread application of C₃N₅ by combining knowledge from fields such as chemistry, materials science, and engineering.

7. Review the paper for its typological and grammatical mistakes i.e. (Start of the abstract).

Reponse: Thank you so much for your thoughtful feedback on the paper. I truly appreciate your insights and will carefully review the abstract to identify and correct any typographical and grammatical errors. My goal is to enhance the clarity and coherence of the sentences while ensuring consistent terminology and formatting. Your guidance is invaluable, and I will implement these changes promptly to improve the overall quality of the paper. The specific changes are as follows:

Line 7-19:Piezoelectric catalysis has shown great potential for application in green chemistry due to its "clean" properties. By applying external mechanical force, this method can induce rapid charge transfer, providing an important reaction pathway for carbon neutrality and carbon peaking. Carbon nitride (C₃N₅) based catalysts, as a novel material, have received widespread attention for their synthesis and application in piezoelectric catalytic degradation of organic compounds. This review summarizes the latest research progress of C₃N₅ based catalysts, covering their applications in environmental governance and resource utilization, including the removal of organic pollutants in water. We focused on the synthesis strategy, characterization methods, and application progress of C₃N₅ based catalysts in the degradation of organic pollutants. Quantitative results showed that some C₃N₅ based catalysts had removal efficiencies of over 85% in the treatment of specific pollutants. In addition, this article also discusses the piezoelectric effect and its degradation mechanism, providing direction for future research. Finally, the application prospects and potential development directions of C₃N₅ based catalysts in environmental governance were discussed.

8. Review the caption of figures 4, 5 and 6.

Reponse: Thank you for the reviewer's attention to the titles of Figures 4, 5, and 6. We will carefully review the titles of these charts and ensure that they more clearly reflect the content of the charts and their relevance to the research. In the revised version, we will make necessary modifications based on the suggestions of the reviewers to improve the readability of the charts and the accuracy of information communication. Thank you again for your careful review of our work.

Line 380-390: Figure 4. The influences degradation, including: (a) SPC concentration, (b) U-C₃N₅ dosage, (c) initial pH of SMZ solution, (d) anions, and fulvic acid., (b) and (d) SPC concentration and U-C₃N₅ dosage. Test bar Piece :CMZ, initial 10mgL-1, T= 250.5 °C, visible light ⁴.

Line 320-321: Figure 5. Co-C₃N₅ activates PMS for PCB28 degradation: (a) degrade kinetics, (b) The catalytic ability of Co-C₃N₅ to PCB28 after four cycles[17].

Line 347-349: Figure 6. The effects of Co CsNs loading (a) PMS concentration, (b) and initial reaction pH, (c) on the degradation of PCB28 by Co CsNs/PMS. Reaction Conditions: [Co CsNs = 1.0g L^-1, [PCB28]=0.5 mg L^-1, [PMS] = 0.5-3.0 mM, pH = 3.0-1.0 (buffer solution) [17].

Yin et. al. reported the manuscript which consists of C₃N₅ based material, showing degradation of organics. The material acts as piezoelectric catalyst. Flow of presentation is fine. However there is major scientific flaws. Thus I believe that major revision is necessary before taking any decision . Some of the flaws are mentioned below for authors' guidance.

1) There is no experimental section in this manuscript. Thus reproduction the result and future application, it is very difficult. Therefore authors should write synthesis details and experimental set up in details for each of the study.

Reponse: Thank you to the reviewer for their careful review and feedback on our manuscript. We understand that there are indeed difficulties in replicating results and future applications without an experimental section. Therefore, in the revised version, we have cited the literature mentioned in each study, which reports the synthesis details and experimental settings of the materials. Thank you again for your suggestions. We will strive to improve the quality of the paper.

2) Authors have mentioned that they have done AIMD calculation for confirming the stability. However there is no supporting data for this calculation.

Reponse: Thank you to the reviewer for their careful review and feedback on our manuscript. We recognize that the lack of supporting data in AIMD calculations can indeed affect the persuasiveness of the results. In the revised version, we will supplement relevant supporting data, including the detailed process of AIMD calculation. We greatly appreciate your suggestions and will strive to improve the quality of the paper.

Line 347-349: First principles calculations are performed using the Vienna ab initio simulation package (VASP) based on density functional theory (DFT). The electron ion interaction is described by the Projection Enhanced Wave (PAW) potential, using the Perdew Burke Ernzerhof (PBE) form of Generalized Gradient Approximation (GGA) as the exchange correlation functional, and introducing the DFT-D3 functional to consider van der Waals interactions, in order to effectively reproduce the lattice constants in the experiment. HSE06 hybrid functionals are used to provide more reliable electronic band structures and light absorption properties. The Kohn Sham electron wave function is developed using a 520 eV plane wave, with energy convergence set at 10^-5 eV and residual force of 0.01 eV Å ⁻¹. The Brillouin zone integration uses a 7 × 7 × 1 k-point grid. To eliminate the interaction between adjacent images, a vacuum space of over 20 Å was applied in the z-direction. The electrocatalytic reaction calculation uses 2 × 2 super units. The formula for calculating the formation energy of C₃N₅ monolayer is Ef=E (C₃N₅) − (m μ C+n μ N), where E (C₃N₅) is the total energy of the monolayer, m and n are the number of carbon and nitrogen atoms per unit cell, and μC and μN are obtained from graphene and N₂, respectively. The photon spectrum is calculated through the Phonopy code and VASP interface, and first principles molecular dynamics simulations are conducted under the gauge ensemble (NVT) with a time step of 1.0 fs ⁵.

3) To confirm the formation of C₃N₅ material, authors should do other spectroscopic characterizations such as NMR, PXRD, FTIR etc. and match with their claim.

Reponse: Thank you so much for your kind suggestion. We truly appreciate your recognition of the significance of additional spectroscopic techniques like NMR, PXRD, and FTIR in confirming the characterization of materials. These methods indeed provide great insights. However, we would like to gently clarify that our paper is a review article that mainly focuses on summarizing and analyzing the existing research rather than presenting new experimental data. As a result, we are not able to carry out these additional characterizations by ourselves. We hope this explanation brings some understanding, and we are really grateful for your understanding and continuous support. Thank you once again for your precious comment!

4) Authors should give comparison table to compare catalytic efficiency of their material in each condition with other reported compounds.

Response: Thank you for your review. Your suggestion is of great significance to the improvement of the quality of our manuscript. This is a review article and we have not synthesized the relevant catalysts ourselves. By reviewing the relevant literature, we collected some relevant literature on the degradation of pollutants by C₃N₅ based piezoelectric catalysts. Specifically as follows：

Catalytic system	Reaction conditions	Target pollutants	Removal efficiency	Ref
RN-g-C3N5	0.02 g RN-g-C3N5 20 Ml 20 mg/L MB	Methylene Blue (MB)	98%(120 min)	6
AgCl/g-C3N5	50 mg AgCl/g-C3N5 50 mL 10 mg/L RhB	Rhodamine B (RhB)	96 % (30 min)	7
CeTiO6/g-C3N5	1.6 g/L CeTi2O6/g-C3N575 mL 10 ppm 2.4-DCP300 W xenon lamp (λ > 420 nm)	2, 4-dichlorophenol (2,4-DCP)	96 % (120 min)	8
CdS/ g-C3N5	0.1 g/L CdS-MHP50 mL 0.01 mM RhB1 sun AM1.5 G	Rhodamine B (RhB)	90 % (80 min)	9
Xp-/g-C3N5	1 sun AM1.5 g 6P-gC3N55 ppm RhB, 20 ppm TC350 W xenon lamp	Rhodamine B (RhB)Tetracycline (TC)	100 % (180 min)	10
Ag3PO4/g-C3N5	1.0 g/L Ag3PO4/C3N550 mL 20 mg/L TCH300 W Xe lamp (λ > 400 nm)	Tetracycline hydrochloride (TCH)	90.5 % (60 min)	11
FeOCl/ g-C3N5	1.0 mg/mL Catalyst75 mL 10 mg/L TC30 % 200 μL H2O2	Tetracycline (TC)	95 % (40 min)	12
CDs/MoS2/g-C3N5	0.02 g/L Catalyst 50 mL 30 mg/L MB300 W Xe lamp (λ > 420 nm)	Methylene blue (MB)	94 % (120 min)	13

 

5) Authors should give plausible mechanism to show how the reported material is acting piezoelectric catalyst for degradation of Rhodamine B.

Reponse: We appreciate the reviewer’s valuable suggestion regarding the need for a plausible mechanism to explain how the reported material acts as a piezoelectric catalyst for the degradation of Rhodamine B. In our revised manuscript, we will include a detailed discussion of the proposed mechanism. By providing this mechanistic insight, we aim to strengthen our argument and clarify the role of the piezoelectric properties in the catalytic process. Thank you for your constructive feedback, which will help improve the quality of our work.

Line 64-66: The principle of ZIF-8 nanoparticles degrading Rhodamine B may be through adsorp-tion and the generation of active substances to react with it and other mechanisms to achieve.

Line 223-237: The principle of the electrocatalytic system effectively interacting with Rhodamine B with the assistance of ultrasound is that ultrasound can promote mass transfer and reaction kinetics, and can also cause physical and chemical effects on the reaction sys-tem, such as generating cavitation bubbles that can enhance the contact and reaction between the electrocatalyst and RhB.

6) To check the recyclability of the material, authors should study PXRD and FTIR after each cycle, to examine the status of the material.

Reponse: Thank you for your comments. Your comments are very helpful to improve the quality of the manuscript. So sorry, we only found the SEM images after the relevant recycling, and we could clearly see the cracks on the surface of C3N5 after the reaction.

 

The SEM of C₃N₅ reaction diagram after the cycle

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Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No further comments

Reviewer 2 Report

Comments and Suggestions for Authors

Authors have done sufficient improvement in the revised manuscript 

Reviewer 4 Report

Comments and Suggestions for Authors

I think that the present review paper was significantly improved after the reviewers comments were addressed. It does not look out as a compilation any more.

I recommend acceptance in the present form