Zinc incorporated covalent organic framework (Zn@DBPG): an efficient catalyst for the synthesis of carbamates through CO2 and non CO2 fixation pathways under sustainable condition

Abstract

Recent trends in synthesis of organic fine chemicals using metal incorporated covalent organic frameworks as heterogeneous catalyst clinching appreciable attentions towards researchers. Permanent porosity, high surface area and extremely thermal stable nature makes those covalent organic frameworks (COFs) based materials as appropriate heterogeneous catalyst. The amine-aldehyde modified covalent organic framework constructed zinc catalyst; Zn@DBPG is synthesized and characterized properly. The synthesized material is utilized as an efficient catalyst for the production of organic carbamates following two different pathways: one is carbon dioxide fixation path and another is non carbon dioxide track under mild reaction conditions. In CO2 fixation track, both alkyl halides and aryl halides produced carbamates by reacting with various aromatic amines in presence of Zn@DBPG at room temperature. The absence of a solvent makes this catalytic process more environmentally friendly and greener. Besides, organic carbamate synthesis in non CO2 pathway environmentally benign urea is employed instead of CO2. Aliphatic as well as aromatic alcohols smoothly undergo through this catalytic reaction in ambient reaction conditions. High yield of respective carbamate products are obtained through both catalytic reaction pathways. Again easily separable COF catalyst Zn@DBPG perpetuates its catalytic productivity even after usage of seven catalytic reaction cycles. Besides, feasible mechanism cycles of the catalytic reactions in both pathways established here by DFT calculations.