Co(II)-embedded covalent organic framework for catalyzing CO2 fixation to highly valuable N-formamides and 2-oxazolidinones under mild conditions

Abstract

Turning carbon dioxide (CO 2 ) into useful substances, such as fuel and chemicals, offers a clear way to lower the amount of this greenhouse gas in the environment. In the present scenario, COFs (covalent organic frameworks) provide tremendous potential for CO 2 fixation. Accordingly, a hydroxyl-rich EtDh-COF was constructed through Schiff-basecondensation using 4,4′,4″,4′″-(ethene-1,1,2,2-tetrayl)tetraaniline (Et-NH 2 ) with 2,5 dihydroxyterephthalaldehyde (Dh-CHO). The prepared EtDh-COF possesses an abundant number of imine and hydroxyl groups, facilitating the easy grafting of non-noble Co(II) ions to acquire Co-COF, which was subsequently applied to formylate various amines to valuable N-formamides utilizing CO 2 as a C-1 feedstock with phenylsilane as the reductant. Moreover, the effective conversion of propargylic amines into 2-oxazolidinones, valuable bioactive commodity chemicals, has also been accomplished by consuming carbon dioxide. Notably, Co-COF displayed excellent catalytic activity for producing formamides and 2oxazolidinones, which serve as crucial precursors for pharmaceuticals, agrochemicals and other bioactive substances. Moreover, Co-COF can be easily recycled for multiple runs without losing scaffold stability and catalytic activity. Thus, this work demonstrates the sensible design of Co-COF for the efficient use of CO 2 to produce two useful products, Nformamides and 2-oxazolidinones, under mild conditions.