Reversible and Irreversible Laser Interference Patterning of MOF Thin Films

Round 1

Reviewer 1 Report

This manuscript demonstrated that reversible and irreversible interference patterning on metal-organic framework (MOF) thin films. The reviewer cannot recommend to published in Crystals because of the following reasons.

1. The reviewer cannot catch up the importance of the patterning on MOF films and the reason why MOFs are considered as an ideal model crystal from Introduction section. What applications are envisioned with MOF patterning? Does the application have to be using MOF?

2. The experimental procedure lacks the information on HKUST-1 precursor concentration and the laser irradiation time.

3. The reversible patterning are not proven from the manuscript. At least, the pictures before and after certain time from pattering should be provided. If possible, the results of physicochemical analysis are also provided.

4. In Figure 3, what does the horizontal axis means? It should be added the title and scale. The caption of this figure

5. How to estimate irradiation power in line 142-144? Please explain more.

 

Minor comments:

 

Line 145 “20 times 20 times” -> “20 times”

Author Response

Reply:

- English language and style are fine/minor spell check required

Checked and corrected.

- Does the introduction provide sufficient background and include all relevant references?

We've improved the introduction through expanding the description of MOFs as important materials for laser patterning with corresponding new references [17-24].

- Is the research design appropriate? and Are the methods adequately described?

We have added the PXRD measurement details, as well as laser parameters for interference patterning (highlighted in yellow).

- Are the results clearly presented?

The text of abstract, introduction and conclusion has been improved following the strategy to clarify the results.

- The reviewer cannot catch up the importance of the patterning on MOF films and the reason why MOFs are considered as an ideal model crystal from Introduction section. What applications are envisioned with MOF patterning? Does the application have to be using MOF?

We really missed this important point in the introduction. New version of the text (highlighted in yellow) reflects the importance of MOFs for laser drawing with additional references [17-24].

- The experimental procedure lacks the information on HKUST-1 precursor concentration and the laser irradiation time.

The MOF (HKUST-1) has been synthesized from a mixture of Cu(NO₃)₂ and BTC (i.e., 1,3,5-benzenetricarboxylate) in ethanol. The final composition of HKUST-1 is Cu-BTC. Data on precursors, as well as laser illumination parameters, are given in the new version of the manuscript (highlighted in yellow).

- The reversible patterning are not proven from the manuscript. At least, the pictures before and after certain time from pattering should be provided. If possible, the results of physicochemical analysis are also provided.

The description of the reversible pattern and a new figure (Figure 3e) have been added to the new version of the text. We have also confirmed experimentally (by Raman and reflection spectroscopy) that the film returns to its original state after the reversible laser patterning. However, in order not to give the same "before and after" spectra, we referred to our earlier work [26] where these measurements have been made.

- In Figure 3, what does the horizontal axis means? It should be added the title and scale. The caption of this figure.

The figure itself and the figure caption has been improved.

- How to estimate irradiation power in line 142-144? Please explain more.

We apologize for the poorly written text. The description of the laser intensity estimation has been improved (highlighted in yellow in the new version of the text).

- Line 145 “20 times 20 times” -> “20 times”

Corrected.

Reviewer 2 Report

Work describes patterning of the MOF thin films in a reversible and irreversible manner using interference of incident laser. While the paper itself is interesting I would as authors to stress the differences benefits and improvements of their work in respect to work of e.g. H. Deng https://pubs.acs.org/doi/10.1021/jacs.9b00355 especially in the aspect of the irreversible patterning, as this seems entirely missing.

11)     Page 1 lines 39-40, authors write “Nevertheless, this concept has not been still implemented for MOFs.”. What is it meant here? That the patterning by interference was not demonstrated in MOFs? If yes I would ask for a small comment why that would be beneficial in comparison to the work of Deng.

22)     PXRD patter on Figure 1 is not informative. I would appreciate if authors would stack it with simulated pattern from the literature ( e.g. FIQCEN https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=112954&DatabaseToSearch=Published). In addition, the diffraction pattern presented in the paper and that in the reference 20 from which authors took the indices differ significantly in terms of peak intensity. This suggests substantial preferred orientation of the crystallites. Similarly, there is an intense reflection located at smaller angle than (200) without index, not present in the PXRD patterns from ref. 20. Is it possible that this reflection stems from (111) planes which should be located at ca. 5.8 2Θ? Simulation of the PXRD pattern can be conveniently performed e.g. in Mercury freeware while simulation of the PXRD pattern with preferred orientation unfortunately only in the paid version. In addition, stacking of the patterns would allow referees and readers to judge on the phase purity of the film, in terms of small molecules .

33)     Authors go into a great detail in the description of the experimental setups without even a small mention of diffractometer. I would ask authors to provide details on the instrument and measurement geometry (Bragg-Brentano?)

44)     On the optical micrograph in Figure 1, MOF thin film doesn’t look very homogenous. However, it’s quite difficult to make nay judgment due to the poor quality of the photo. I would appreciate any comment from the authors on the morphology and the quality of the film.

55)     Page 3 lines 96-98 authors wrote” In contrast, the latter mode (irreversible one) is related to thermal decomposition of HKUST-1 with releasing of copper encapsulated in amorphous carbon [19,22].” None of these references deal with the topic. Reference 19 describes stability to the water vapour while 22 deals with the decomposition under electron beam. I would ask authors to provide correct references e.g. reference 11.

66)     Regarding the reversible transformation originating from laser-induced water desorption. Authors back-up the claim with the reference to their work, where they study in detail this phenomenon in crystals. However, nowhere in the current work it is demonstrated that the reversible process is truly reversible in the films. Additional optical micrograph showing regenerated film should suffice to convince referees and readers.

77)     Regarding the irreversible transformation, page 4, lines 113-114 authors write “Using this system we have mapped the coordination-bond breaking (peak centred at 240 cm−1)” I presume Cu-O(carboxylate) is meant here? Which mode would that be? In principle Cu-O(water) stretching is located at ca. 280cm-1, Cu-Cu in evacuated HKUST is at 224 cm-1 (values from ref 16, author’s work). I would appreciate if the authors could be more specific and provide reference, and comparison Raman spectra of pristine and decomposed areas in Figure 3.

88)     Figures 4 a,d,g,c,f,i are not referenced in the text I believe a,d,g panels belong to page 5 line 132 mention of Figure 4

99)     Page 5 lines 141-144. The sentence is unreadable, I have impression that I understand it and what author mean is below 11.1 μW μm^-2 there is no patterning, above 0.22 mW μm^-2 irreversible patterning and between these two thresholds reversible patterning is occurring?

110)  Speaking of which, there are multiple instances on page 4 where instead of μ the authors use u so uW, um. I would greatly appreciate if that would be corrected.

111)  Page 4 line 145 “ (…) 20 times 20 times (…)”- repetition

Author Response

Reply:

- Moderate English changes required

Checked and corrected.

- Does the introduction provide sufficient background and include all relevant references?

We've improved the introduction through expanding the description of MOFs as important materials for laser patterning with corresponding new references [17-24].

- Are the results clearly presented?

The text of abstract, introduction and conclusion has been improved following the strategy to clarify the results.

- I would as authors to stress the differences benefits and improvements of their work in respect to work of e.g. H. Deng https://pubs.acs.org/doi/10.1021/jacs.9b00355 especially in the aspect of the irreversible patterning, as this seems entirely missing.

The key difference between our work and H. Deng (https://pubs.acs.org/doi/10.1021/jacs.9b00355), as the Reviewer rightly noted, is the combination of a reversible and irreversible patterning. As for comparing our results of the irreversible pattern with H. Deng, both the drawing speed (the drawing is created in one click) and the spatial resolution are a clear advantage. We have reached 5 µm period of the laser patterning, while H. Deng achieved just 100 µm (see Figure S5). However, we have tried to describe clearly our advantages in the abstract and conclusion, avoiding gross underestimation of the importance of pioneering work of H. Deng.

- Page 1 lines 39-40, authors write “Nevertheless, this concept has not been still implemented for MOFs.”. What is it meant here? That the patterning by interference was not demonstrated in MOFs? If yes I would ask for a small comment why that would be beneficial in comparison to the work of Deng.

We've improved this part of introduction through expanding the description of MOFs as important materials for laser patterning in a single-step process (in contrast to multi-step laser metallurgy) with corresponding new references [17-24].

- PXRD patter on Figure 1 is not informative. I would appreciate if authors would stack it with simulated pattern from the literature ( e.g. FIQCEN https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=112954&DatabaseToSearch=Published). and Similarly, there is an intense reflection located at smaller angle than (200) without index, not present in the PXRD patterns from ref. 20. Is it possible that this reflection stems from (111) planes which should be located at ca. 5.8 2Θ?

This is a very useful remark and we agree with this comment. Figure 1 has been updated with a reference spectrum CCDC=112954 that shows all the peaks we see, including the low angles. However, we cannot speculate in this work about the ratio of peak intensities associated with the specific orientation of HKUST-1 nanocrystals, since this aspect does not affect the result of the laser patterning, but requires additional structural analysis.

- Authors go into a great detail in the description of the experimental setups without even a small mention of diffractometer. I would ask authors to provide details on the instrument and measurement geometry (Bragg-Brentano?)

We have added the detailed description of the PXRD measurements within the new version of the text.

- On the optical micrograph in Figure 1, MOF thin film doesn’t look very homogenous. However, it’s quite difficult to make nay judgment due to the poor quality of the photo. I would appreciate any comment from the authors on the morphology and the quality of the film.

We have added a higher quality film image. But it is worth saying that the film of 2 um thick does not look quite uniform: There are torn borders and a slight fluctuation in thickness leading to inhomogeneous picture.

- I would ask authors to provide correct references

Indeed, in a number of cases we have made mistakes with incorrect references. In the new version of the text, new required references have been added and their correct position in the text has been checked.

- Nowhere in the current work it is demonstrated that the reversible process is truly reversible in the films.

The description of the reversible pattern and a new figure (Figure 3e) have been added to the new version of the text.

- I would appreciate if the authors could be more specific and provide reference, and comparison Raman spectra of pristine and decomposed areas in Figure 3.

Updated Figure 3, reflecting Raman changes, and related description have been added in new version of the text.

- Figures 4 a,d,g,c,f,i are not referenced in the text

Fixed. See the new version of the manuscript (highlighted in yellow).

- Page 5 lines 141-144. The sentence is unreadable

We apologize for the poorly written text. Please see the new version of the manuscript (highlighted in yellow).

- Speaking of which, there are multiple instances on page 4 where instead of μ the authors use u so uW, um. I would greatly appreciate if that would be corrected.

Improved.

- Page 4 line 145 “ (…) 20 times 20 times (…)”- repetition

Corrected.

Round 2

Reviewer 1 Report

This manuscript has been sufficiently revised.

Therefore, the reviewer recommends this manuscript to be published in Crystals.