Facile Synthesis of COF-Supported Reduced Pd-Based Catalyst for One-Pot Reductive Amination of Aldehydes

Round 1

Reviewer 1 Report

The manuscript describes the synthesis of a Pd-based catalyst using a COF as support, and its use in an efficient and very convenient one-pot reductive amination of up to 27 different aldehydes. The characterization results and catalytic studies are sound and coherent. I believe this work is of interest for the audience of Catalyst journal and therefore I recommend its publication after minor considerations are addressed.

1) Figure 3b. The PSD shows higher adsoprtion capacity associated to 30 - 60 nm pores for the COF before the insertion of Pd nanoparticles. This makes no sense, as this should be otherwise due to Pd nanoparticle blocking of the COF pores. Can the authors make a comment on this? Are the graphs correctly labeled?

2) Even though the reciclabiity of the catalyst is not explored in this work, do the authors observed Pd leaching in reaction media after catalyses?

3) Scheme 2. The authors claim that 1c->1b reaction is catalysed by Pd-SJ04 catalyst, the same way as those reactions involving small molecules (H2, NH3). Is there a proof of this? maybe the catalyst dont play a key role in this reaction and should be removed from the equation

4) Minor considerations on writing style and grammar (please revise for additional minor errors throughout the paper):

- line 11 (abstract): “pharmaceutical industries” instead of “pharmaceuticals industries”

- line 59: “benzylamine and dibenzylamine as products” instead of “product benzylamine and dibenzylamine”

- line 63: “an in situ-generated” instead of “an in the situ-generated”

- line 94: “catalyst supports” instead of “catalyst supporters”

- line 96: “have” instead of “has”

- line 97, 194: “support” instead of “supporter”

- line 100: “COFs were” instead of “COF was”

- line 154: “room temperature” instead of “temperature”

- section 2.3: the “Tristar 3010 isothermal nitrogen sorption analyzer” is mentioned twice

- Fig 1: “pattern of the” instead of “pattern and of the”

- Table1: “Temperature” instead of “Tempreture”

- line 287: “seemed very difficult” instead of “seemed to very difficult”

Author Response

Dear  reviewer,

Thank you very much for your comments. We revised the whole manuscript following your suggestions. Here, we provide a point-by-point response to your comments.  "Please see the attachment." 

Best wishes

Jianguo Liu

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript submitted by author related to Facile Synthesis of COF Supported Reducibility Pd-based catalyst for One-Pot Reductive Amination of Aldehydes is an interesting work with some good finding. But manuscript need to be rigorously revised in order to publish the work in catalysts Journal.

1. Abstract section need modification. Author have mention Pd-SJ04 catalyst under this section. What does it means need to be express clearly? Under this section kindly briefly describe your methodology and Clearly describe the most important findings of your study.
2. Try to avoid the abbreviation under abstract section. Such as “COF material”? Provide the full form once.
3. In page 1 introduction section, author have mention the sentences “Reductive amination of carbonyl compounds using transition-metal catalyst has become a highly versatile and robust method for various transformation in the C-N bond construction, due to its obvious advantages such as mild reaction conditions, wide availability, and inexpensive reagents”. However, authors provide no relevant references in support of these sentences. Kindly add the references.
4. Author have said “Moreover, the activation of H2 and the catalytic reduction of unsaturated compounds is a fundamentally promising environmentally friendly process”. Justify this statement.
5. Author mention in page 2, “For example, Gu and co-workers[3] developed the selective synthesis of secondary amines through direct reductive amination of aldehydes using the unsupported Pt nanowire catalyst under mild reaction conditions. They found that the dibenzylamine selectivity increased and dibenzylimine selectivity decreased when the reaction temperature increased” Provide some numerical data in there discussion about the reaction conditions, selectivity and catalytic efficiency?
6. Line 83 “The Pt catalytic activity and stability were enhanced by the incorporation of Mo into Pt. H2 can migrate from the surface of Pt sites over to the Mo species, liberating the Pt active sites.” Justify this statement.
7. Page 3, Scheme 1. Methodologies for the selective production of amines via various transition metals based catalytic systems. Is it author own protocol or adopted from literature.
8. In page 4 section 2.2. Catalyst preparation, 2.1. Synthesis of COF material. Is it protocol authors own or adopted from literatures. If so kindly, provide the reference in support of method.
9. In section 2.2.3. Synthesis of the reduced COF based Pd catalyst, how the Pd (OAc)2 and SJ02 concentrations and different ration impact the final efficiency of catalyst.
10. In page 5, Section, 2.4. General procedure for catalytic reductive amination reaction, how author have optimized this conditions, optimization study are missing in this script.
11. In line 209, author have mention under results and discussion of XRD “the peak at 6.4° is originally derived from COF support SJ02, and the relatively broad signal at around 26.3° matches well with the (001) reflection, which can be ascribed to the π−πstacking between ordered adjacent layers of COF sheets.” Provide the JCPDS number and reference to support of the above sentence.
12. In page 6 Figure 1. FTIR spectra and XRD pattern and of the SJ02 and Reducibility Pd-SJ04. I can see two figures are there with a and b. but in caption of Fig.1 a and fig.1b is not mention. Need to be corrected.
13. In page 6, line 215, author have mention “Meanwhile, as shown in Figure 2, Reducibility Pd-SJ04 exhibits a uniform spherical morphology with an average size of about 100 nm” But while observing the SEM image (a), I cannot find the spherical morphology. This images need to be replace or change the morphology in text.
14. Provide the EDS composition to confirm the % weight of each element present in Pd-SJ04.
15. Figure 4. (a)The survey spectra and (b) high-resolution XPS spectra of Pd3d for Reducibility Pd-SJ04. No explanation about N1s and O1s are discussion in the text.
16. The manuscript was very poorly written. Need the English native speaker to correct the language of the script completely.

Author Response

Dear Reviewer,

Thanks for your consideration and comments. We corrected the whole manuscript and now upload a point-by-point response to your comments.

"Please see the attachment."

Best wishes,

Jianguo Liu

Author Response File: Author Response.pdf

Reviewer 3 Report

The work here presented represents an interesting research on the application of heteregeneous catalysis in the field of organic synthesis. Its major novelty seems to be the proposal of a more sustainable and environmentally friendly synthetic route, so it deserves in principle an opportunity for publication. However, there are many deficiencies that must be corrected before, as follows:

Major deficiencies 

1) Throughout the whole text the authors employ wrongly the term "reducibility". It should be "reduced". Reducibility is a property, not a state or condition. I also suggest to refer to the catalyst as "COF-supported" (with the dash symbol).

2) Regarding the samples nomenclature, why did the authors use SJ02 and Pd-SJ04 for the support and catalyst, respectively? In line 150 they talk about the acronym SJX, so does this mean that SJ01, Pd-SJ01, Pd-SJ02 and Pd-SJ03 samples were also (at least) prepared? If so, where can the reader find information about these samples??? The reader can think that perhaps they are available in the supporting information, mentioned by the authors at the end, but the truth is that no supporting information was provided with the submission either!

3) Information related to the textural analysis is full of confusing aspects. First of all, in the experimental section, what instruments was employed, a Quantachrome or a Micromeritics? In addition, information related to the latter is repeated. Concerning the results obtained by N₂ physisorption, the authors should indicate why the hytheresis loops in the isotherms (Figure 3a) do not close. If they did, what would it be the type? On the other hand, the authors did not comment (nor explained why) Pd incorporation decreased BET surface area. Moreover, being this the effect, why the pore size distribution curves are so similar in Figure 3b, and even more pores with 60 nm size developed in the Pd-containing sample? I suppose the volume of micropores decreased in this sample as well but the authors did not mention anything about, and they should.

4) The main deficiency among all is the lack of quantitative analysis. Information about the amount of the active phase (in this case Pd) in the catalyst is missing and this is crucial for any heterogeneous catalyst. How much Pd were the authors able to introduce in the support through their preparation? Providing this information is absolutely mandatory.

Minor deficiencies (in the order of appearance):

Line 14: bigger letter size for covalent organic framework

Line 16: avoid sample nomenclature in the abstract

Line 19: "support" should be "supported". Also, insert blank space before the parenthesis.

Line 49: According to the references list, Gu and co-workers should be Qi et al.

Line 52: dibenzylamine cannot increase and decrease at the same time!

Line 56: indicate the meaning of GC (gas chromatography) the first time the acronym is used.

Line 59: The correct sentence would be "can give benzylamine and dibenzylamine as products".

Line 62: According to the reference list, Darcel and co-workers should be Zhang et al.

Line 63: The correct sentence would be "hydrosilation using an in situ-generated…" 

Line 75: Osakada et al.

Line 76: According to the references list, Gu and co-workers should be Lu et al.

Line 86: Insert "it is" before "active"

Line 89: Scheme 1 was not introduced in the text !!!

Line 93: The correct sentence would be "As it is well-known, the catalyst support…"

Line 95: Move "singnificantly" to position after "affect" in line 94.

Line 97: "They were" instead of "it was"; and Yaghi and co-workers should be Cote et al., according to the reference list

Line 98: "They have" instead of "It has", and "their" instead of "its"

Line 100: a COF

Line 108: immobilized in COF materials

Line 112: amides ???!!!

Line 146: "in the presence"

Line 162: "were" instead of "are"

Line 164: "was" instead of "is"

Line 166: "acquired" instead of "determined"

Line 167: "studied" instead of "calculated"

Line 175: for the catalytic

Line 185: "gas chromatography" or "GC" instead of "GC chromatography"

Lines 189-198: move this paragraph to the experimental section

Figure 1 caption should say "FTIR spectra and XRD patterns of SJ02 and reduced Pd-SJ04"

Figure 2 caption should say "SEM image (top) and EDS mapping (bottom) of reduced Pd-SJ04"

Line 220: Insert scale bar in Figure 2b.

Line 230: cancel "two"

Figure 4 caption should say "(a) The survey and (b) Pd3d high resolution XPS spectra corresponding to Pd-SJ04. The survey spectrum of SJ02 is also included as a reference sample".

Line 236: "spectra" instead of "curves"

Line 240: Insert "and" after "catalyst,"

Line 241: "spectrum" instead of "spectra"

Line 249: The correct sentence would be "As it is well known, Pd⁰ like Pd/C has a..."

Line 251: The correct sentence would be "Generally speaking, H₂ pressure is a key factor, which can influence…"

Line 259: 83.8% instead of 87.6 % (this value is obtained at 70 ºC, not at 90 ºC). By the way, any explanation for the fact that 70 ºC is the optimum temperature? Expected evolution could be increasing or decreasing selectivity with temperature depending on the endothermic or exothermic character of the reaction.

Line 294: Inster blank space before parenthesis.

Line 315: "using the" is written in bold type letter.

Line 319: insert comma before "dibenzylamine"

Line 321: "have" instead of "had"

Lines 322 and 325: cancel "And"

line 323: The correct sentence would be "The latter showed …"

References: The format should be uniform. It has no sense that only one author name is indicated in general (using et al. for the rest), even more when the authors do not follow this criterium in refs. 14, 18, 19, 20, 21, 25, 28 and 29.

Line 356: RSC

Line 359: A

Line 366: ACS

line 381:  Journal of Catalysis

Line 398: ACS

 

 

 

 

 

Author Response

Dear Reviewer,

Thanks for your consideration and comments. We corrected the whole manuscript and now upload a point-by-point response to your comments.

"Please see the attachment."

Best wishes,

Jianguo Liu

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have satisfactorily revised the script.

Reviewer 3 Report

The authors considered all my comments and suggestions, and they made corrections accordingly. The manuscript can now be acccepted for publication. Please, be sure first to correct the following typo: In page 6, line 167, "matix" must be "matrix".