A Highly Efficient Bifunctional Catalyst CoOx/tri-g-C3N4 for One-Pot Aerobic Oxidation–Knoevenagel Condensation Reaction
Round 1
Reviewer 1 Report
The authors report on an interesting study on the synthesis and use of a bifunctional heterogeneous catalyst for a one-pot oxidation-Knoevenagel condensation reaction. The catalyst is a composite material of graphitic carbon nitride and cobalt(II) oxide. This material has been tested in a aerobic oxidation-tandem Knoevenagel condensation of benzyl alcohol and malonodinitrile, with excellent results. Reusability has been test up to 4 cycles, with a slight decrease in conversion (from 96.4% to 84.9%). Due to the recent attention paid to catalytic materials based in graphitic carbon nitride, this contribution is of interest to a variety of readers. I suggest however that some general references on g-C3N4 are added (Nanosacale 2015, 7, 15; Nanoscale 2019, 11, 14993; Nyomori et al. 2020, Critical Reviews in Solid State Materials Science...), especially in order to clarify some structural aspects (s-triazine-based catalyst vs. heptazine based ones) to the general reader.
It would be also interesting if the authors could comment on the scope of this method (use of substituted electron-rich or electron-poor benzyl alcohols, and of other malonate derivatives).
Author Response
Three general references on g-C3N4 suggested by the reviewer are added. Three other references (ref. 28-30) on s-triazine-based carbon nitride were also added in order to clarify some structural aspects to the general reader.
According to our previous study (ref. 27), the Co3O4/g-C3N4 composites are good catalysts for aerobic oxidation of various aromatic alcohols though aromatic alcohols bearing-electron withdrawing groups are more difficult in formation of the corresponding aldehyde than those with electron donating groups. The present catalyst is believed to be active for aerobic oxidation-Knoevenagel condensation of various aromatic alcohols besides benzyl alcohol. This was added in line 194 to comment on the scope of this method.
Reviewer 2 Report
Yue and co-workers describe the development of a novel bifunctional catalyst consisting of supported cobalt oxide. It shows optimum performance in a tandem aerobic oxidation-Knoevenagel condensation. It can be recycled and reused withouth jeopardazing its activity. The work is clear and well presented.
Admitedly it has some elements of novelty and, as a consequence, merits publication. However, the authors must know that there are other trillions of catalysts capable of doing the same transformation, even with better performance and under milder conditions.
Please remove line 252: the catalyst, precious or not, is certainly metal-based. Also some language polishing is neccessesary.
Author Response
The reviewer is right that there are many catalysts capable of doing the same transformation. However, only a small portion was studied in one-pot reaction using oxygen as oxidation agent. To express more accurately, “under milder reaction condition” in line 191 has been changed to “under mild reaction condition”.
“This precious metal-free catalyst” in line 251 has been changed to “This catalyst”. Language polishing has been done.
Reviewer 3 Report
The present paper describes an interesting combination of inorganic and organic molecules leading to the formation of effective catalyst for Knoevenagel condensation reaction. All the results were presented clearly without any substantial mistakes. Authors should check the text for editorial errors (e.g. 'power' - page 7, line 206 and designation of Celsius degrees in the whole text). After such the corrections I recommend its publication in Catalysts.
Author Response
Word “power” has been changed to “powder”; Designation of Celsius degrees has been corrected in the whole text.
Reviewer 4 Report
This is a well writen paper that accounts for an interesting reaction. The one-pot approach is well described and the results clearly exposed.
The paper merits publication
Author Response
Thank you very much for giving praises to our work.
