Lattice Shrinkage of 2D-COFs under Electron Beam Irradiation

Round 1

Reviewer 1 Report

Ren et al. conducted an experiment investigating the Lattice Shrinkage of 2D-COFs under Electron Beam Irradiation. Their manuscript contains reliable methods and results. I recommend publishing the manuscript as is, except for a small comment on the visibility of subfigures (d) and (e) in Figure 1.

Author Response

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Reviewer 2 Report

The authors report a lattice shrinkage behavior of COFs under electron beam irradiation by comparing the lattice fringes of 2D-COFs under different conditions. By comparing the lattice fringes of TAPT-TFPT COF at room temperature and under liquid nitrogen freezing conditions, they observed lattice fringes that are in good agreement with the PXRD and the theoretical values of COF (2.213 nm) under freezing conditions. However, the lattice fringe spacing was only 1.656 nm at room temperature. However, before accepting the manuscript for publication, some points have to be addressed.

The authors attributed the shrinkage of the structure due to the electron beam damage, ruling out the temperature effect. The imaging conditions were set for low-dose imaging, but did the authors acquired data at lower acceleration voltages? 120 kV or 80 kV. This can provide some information on the type of interaction causing the damage to the COF framework. Perform an experiment at lower voltage. This is important since it can be a guide to minimize the effect when no cryo-TEM is available.

How this radiation damage is compared to the one suffered by zeolites or other soft materials under the electron beam?

Other observations are:

Line 144. Indicate the acquisition time for each image.

Figure 1d,e. Add a coordinated system ab, ac, bc, to help to understand the crystallographic orientation of the stack model. The structure in Figure 1a, it is viewed from "c" orientation?

Line 229. "…can directly observe the hexagonal pores..." In what figure?

Line 224 "…when he first reported the COF structure." add citation.

Lines 230 & 236. The unit cell parameter is 25.38 or 2.538 nm?

Figure 4a: Then, indicate in which direction is viewed.

Line 231. "…the distance from the origin to the 100 crystal plane is 2.16..." where is the origin?

Line 255. What´s the value of shift of the 001 and 100 peaks?

Author Response

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Reviewer 3 Report

The manuscript of Shiwei Ren, Shina Sun, Mingkun Xu, Song Li, Yubing Ding and Mingchao Shao describes a lattice shrinkage of a 2D covalent organic framework (COF) under electron beam irradiation. This phenomenon is reported for the first time. COF, studied in this work, was prepared synthesized by a modified solvothermal reaction at 120 °C using 1,3,5-tris-(4-aminophenyl) triazine (TAPT) and 1,3,5-tris-(4-formylphenyl) triazine (TFPT) as the building blocks and a mixture of dioxane (DO)and mesitylene (MS) as the solvent. TAPT-TFPT COF was characterized by XRD, FTIR, and ¹³C NMR and characterized by argon (Ar) sorption isotherms and TEM. The most interesting aspect of the manuscript is observation of and electron beam-induced lattice shrinkage. It is nice result.

I think that the manuscript is of a high quality; it adds a lot to the existing knowledge on covalent organic frameworks. I recommend acceptance of this manuscript after minor corrections.

1. Please provide an elemental analysis of TAPT-TFPT COF.

2. It is reasonable to provide an explanation of the lattice shrinkage.

Minor editing of English language required.

Author Response

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Reviewer 4 Report

The authors presented very interesting results concerning the problem of determining the parameters of the crystal structure using the electron microscopy method. Indeed, the low degree of crystallinity and small crystal sizes of many MOFs and COFs do not allow using such a standard research method as single-crystal XRD, and also create certain difficulties for PXRD. In this case, TEM can really be the method that could allow determining the parameters of the unit cell of these compounds. Unfortunately, as the authors have shown, the correspondence between the TEM and PXRD data is observed only at low temperatures, while already at room temperature, the cell parameters determined by these two methods differ significantly. This fact shows that when using TEM to determine the cell parameters, it is necessary to maintain a low temperature (liquid nitrogen temperature).

I believe that the article should be accepted for publication. I would just like to wish the authors to introduce a more detailed discussion into the text: 1) the mechanism of action of the electron beam on the substance; 2) if possible, a discussion of which types of MOFs and COFs should exhibit similar effects or this COF has some unique properties; 3) why opposite effects are observed along different crystallographic axes.

Author Response

Good evening. Thank you for your acknowledgement of our work. All the questions about your work are very insightful and interesting. However, many of them cannot be solved by us at the moment 1) the mechanism is particularly unclear, at the moment it is a matter of just discovering the phenomenon, but not giving a reasonable mechanism. More and more of our group's work is currently focussed in this direction in the expectation that a relatively plausible explanation can be obtained in a short period of time; and 2) new systems are still being explored to probe their universality. But at present we have not obtained similar results and repeated out similar phenomena in new materials. Despite the chance, it is still novel and meaningful; 3) We are also very interested in the results of the crystal axis, and more experiments are being carried out in anticipation of a plausible explanation of the problem, and we are also looking for co-operation from other groups, so please feel free to let us know if you have any suggestions!

Thanks again for your understanding and your time.

Best reagrds

Reviewer 5 Report

Manuscript (processes-2610321)

1-    In the introduction, add more studies to highlight the novelty of your study. Cite some studies from the host journal.

2-    In this study, you used TAPT-TFPT COF; explain why?? Especially many studies use different materials, add more information about them, and compare them with other studies.

3-    Write the full name of the TAPT-TFPT COF mentioned first.

4-    Line 91: Cryo-electron microscopy (Cryo-TEM): correct it

5-    Many chemicals used should be listed, and the place purchased.

6-    Write the chemical name of AcOH.

7-    Two models were used, but no more information was mentioned. Please explain in detail all the information about it.

8- Figures 1. & 3 are Unclear; they should be in high quality to be more readable.

9-    Figure 2b has many peaks marked but no information mentioned in the text.

10- Please add a new section about limitations and future aspects to give a clear image for readers about the uncompleted tasks of this study.

Author Response

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Round 2

Reviewer 2 Report

The authors have addressed most of the comments, improving the manuscript. 

Author Response

Thank you for your acknowledgement of our work. Thank you also for your previous useful comments and suggestions, which are insightful and make a lot of sense.

Best regards

Reviewer 5 Report

The authors have satisfactorily addressed all comments made on the original submission. The revised version of the manuscript is recommended for publication.

Author Response

Thank you for your acknowledgement of the research work. Thank you also for your previous useful comments and suggestions, which are insightful and make a lot of sense.

Best regards