Zn(ii)@TFP-DAQ COF: an efficient mesoporous catalyst for the synthesis of N-methylated amine and carbamate through chemical fixation of CO2

Abstract

Selective N-methylation and carbamate formation reactions were demonstrated via the chemical incorporation of CO₂ using a Zn-loaded TFP-DAQ COF (covalent organic framework) as an active catalyst under mild reaction conditions. The selective N-methylation and N-formylation reactions were performed by simply varying the type of solvent. The Zn(II)@TFP-DAQ COF catalyst was characterized via different characterization techniques such as PXRD, FTIR, UV-vis, N₂ adsorption–desorption studies, FESEM and TEM. The catalyst material showed pores in the mesoporous region with a high surface area of 1117.375 m² g⁻¹. The as-synthesized material was applied as a cheap catalyst for the N-methylation of secondary amines and in carbamate formation reactions with high yields of the desired products up to 98.5% and 97%, respectively, with >99% selectivity. The catalyst was found to be completely heterogeneous and reusable for multiple reaction cycles.