Peer review of: Unimolecularly thick monosheets of vinyl polymers fabricated in metal–organic frameworks (2020)

REVIEWER COMMENTS

Reviewer #1 (Remarks to the Author): 

The authors reply for the submitted manuscript "Unimolecularly thick monosheets of vinyl polymers 
fabricated in metal–organic frameworks by Uemura" and coworkers addresses my previous concerns. 
In my opinion the manuscript is suitable to be accepted in Nat. Commun. 

There is only one question left that should be addressed. Why do the authors not include some 
additional comments and discussion including literature as back up from the replies into the 
manuscript? It seems that some points were raised by several reviewers so it would be favorable to 
include some additional text based on the replies to avoid misunderstandings for the reader. 


Reviewer #2 (Remarks to the Author): 

Dear Editor, 
The authors reported a promising method to prepare 2D polymers in MOF cavities, which can be 
widely used to synthesize different 2D polymers. I still hope to see their SEM/TEM images as I 
recommended before. It is very helpful to demonstrate the morphology of their 2D polymer at free-
standing state, sheets or shrink to be balls? Electrons may damage crystallinity of nano-sheets, but 
the main morphology may remain intact. For references, they over-cited papers from the same author. 
This is not good because it has the suspicion of guessing and apple-polishing reviewers. Anyway, I 
fully appreciate its novelty and it can be accepted after revisions following above suggestions. 


Reviewer #3 (Remarks to the Author): 

The manuscript is much easier to read and understand as in its previous form. Thanks to the authors 
for going through this effort. It was worth it. 

There are a couple of remarkable aspects with the science reported: 

1. The construction of a monolayer 2D network with irregular structure (absence of repeat units). This 
is a valuable, everything else but trivial addition to the field of synthetic 2D materials, in particular 
organic 2D materials 

2. The facts that this network with its unprecedented topology consists of structural elements identical 
to those of the mass product polystyrene and that it can be obtained on a useful scale. 
This enables meaningful comparisons with linear and 3D cross-linked polystyrenes, which is the basis 
for finding out what the properties inherent to a macromolecule with 2D topology are like. There is 
practically no knowledge about what to expect from 2D networks, may they be regular (2D polymers) 
or irregular (as described here). Gaining this knowledge is thus of fundamental importance. Having 
even thin stacks of sheets of some 2D material does not help. There is no way around monolayers in 
large quantity. This is what the paper offers. 

3. The finding that the glass transition of the 2D material created is lower than that of reference 
systems and the interpretation that this may be due to the inherent lack of entanglements. 
This relates directly to point 2 and will be of great interest to all those, interested in the viscoelastic 
behaviour of polymeric materials. This observation also urges the question whether the reported Tg difference to the linear material is real. While there is no doubt that the Tg of the linear polymer is in 
the regime of molar mass independence, it is simply unknown whether this is also so for a 2D network 
of the same molar mass. For those the property-molar mass relation may be different. Already the 
fact that this question arises testifies the interest the reported structures will find. 

These three aspects have considerable weight and make clear why this work principally deserves 
being published in Nature Communications. 

Nevertheless, even in the latest version the reviewer feels that the authors could do a bit more in 
terms of describing the network (beyond just the molar mass) and of quantifying more rigorously the 
cross-link density.It would be handy to have an estimate of the the number of cross-links per unit 
area, the average segment length between the cross-links and the estimated lateral extension of the 
unfolded monolayer network. A small graphic showing these features would also be nice (even in the 
main text). 

Concerning the experimental proof for cross-linking density, the authors should please explain the role 
of the very low intensity signals in the 1H NMR spectrum of their network appearing around 5 ppm. 
Even though at first glance one may not realize them, they are there. There should be an insert with 
this region being amplified and, if possible, a signal assignment. It almost looks like as if the cross-
linker had not reacted completely, which may not be a surprise given the narrow confinement. If this 
is so, there will be some dangling acrylate units. They will need to be considered in the structural 
model requested. This would also change the proposed cross-linking degree of 1%. 

Do the authors have an explanation for why the TEM images in Figure S2 are around 50 µm in size, 
while the sizes of the features in the AFM images are much smaller. Shouldn’t they ideally have the 
same size? Please provide a comment. 

Since the whole concept depends on the quality of the MOF mother crystals, it appears appropriate to 
make a few statements on how good these crystals are. Why not showing a reciprocal space 
reconstruction in the SI. Are there no signs of mosaicity? They could question the concept. The 
authors must have all this. Why not showing it? 

In sum, this is a truly excellent paper presenting an exciting new material, which should be published 
after some improvements.