Heterogeneous catalytic carboxylation of terminal alkynes with CO2 over a copper(II)-based metal-organic framework catalyst

Developing efficient, inexpensive and robust heterogeneous catalysts for CO2 conversion is greatly important. In this study, a new stable copper(II)-based metal-organic framework [Cu(Fbtx)2Br2]n (denoted as CZU-7, CCDC-2165700, Fbtx = 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene) was synthesized via a facile and fast microwave heating method. CZU-7 exhibits a two-dimensional layer structure with the 44-sql topology. This material was demonstrated to be an efficient heterogeneous catalyst for the direct carboxylation of 1-ethynylbenzene with CO2, and various propiolic acids were synthesized in moderate to good yields under optimized reaction conditions. Moreover, the catalyst could be easily recovered and reused five times without significant loss of catalytic activity.