Peer review of: Imaging spatiotemporal evolution of molecules and active sites in zeolite catalyst during methano (2020)


RR2
REVIEWERS' COMMENTS:
Reviewer #1 (Remarks to the Author):
  The authors did a thorough job of adapting their paper to the many comments, increasing its
 clearness and accuracy.
 The first 2 responses to reviewer n° 3, I cannot check since they are not in my field of expertise (and
 the addition of Fig 2).
 In some captions, they mention:
 "The error band is standard error of simulation results."
 this is explained in the letter to the reviewers, but may not be clear to the reader. Perhaps explicit
 where the error originates?
 Apart from that the work is excellent and ready for publication in my opinion.
Reviewer #2 (Remarks to the Author):
Reviewer #3 (Remarks to the Author):
  Authors have very carefully answered all comments of all three reviewers and they have made major
 changes to both, main text and supporting information. I believe that all answeres as well as
 modification of the text (and figures in particular) are sufficient and I can recommend the manuscript
 for publication in its present form. In particular I am satisfied with improved description of "deep data"
 approach and with the section on assignemnt of excitation and emission energies based on TDDFT
 calculations.
  I have been through the revised version of the article entitled ‘Imaging spatiotemporal evolution of
 molecules and active sites in zeolite catalyst during methanol-to-olefins reaction’ and would like to say
 firstly that the authors have clearly spent a lot of effort on updating the manuscript taking into
 account the feedback from the first round of reviewing and this has resulted in a more considered
 piece of work. I have though the following comments that require addressing before I think it can be
 published:
 1) The TDDFT section is a welcome addition to the manuscript although the nomenclature used to
 identify the various species present in the sample is unclear to a non-expert like myself. For example
 in the supplementary information, Table 5 and according to the explanation proffered on page 26, I
 interpret a B2+ species to be a napthenic species (i.e. 2 Benzene molecules). However there are N0+
 species assigned so I am not sure what B2+ is supposed to signify. I presume (methyl?) substituted
 benzenes but this needs to be better articulated.
 2) Although there is more welcome information on how the SIM data were accumulated it is still not
 clear what the time difference was from when the SIM measurements were performed and how long
 samples had been exposed to the atmosphere after being removed from the MTO reactor. As I
 mentioned in the first round of reviewing, we have seen that such species will react with O2 and
 whatever else is in the air and that this changes their composition, ergo their emission response. And
 of course this will undermine the findings of this study (note in the study of Borodina et al. the
 implication according to the TOC/Figure 1 is that the samples are interrogated in situ i.e. from within
 the reactor and whilst there are changes as a function of temperature, there is no evidence that the

 same changes occur on exposure to an oxidising atmosphere). However, I think it is unfair to ask the
 authors to solve this problem as it is very challenging and beyond the scope of the study and that the
 real value of these results is that it serves as a demonstrator case. Besides which there has been a lot
 of effort to cross correlate the findings from SIM with other data (modelling, UV-Vis). I do think
 though that some comment regarding the time taken to acquire the SIM data and the time the
 samples were exposed to the air should be included lest others who embark on similar studies will end
 up laboring under the false pretense that all that is required is a SIM setup + few reacted samples. My
 PhD student who has performed similar studies in the past would argue that unless the atmosphere
 was controlled, then what you are measuring are not the species that are present during the reaction.
 Fortunately she is not reviewing this manuscript.