Bifunctional Metal-Free Porous Organic Framework Heterogeneous Catalyst for Efficient CO2 Conversion under Mild and Cocatalyst-Free Conditions

To reduce the ever-growing greenhouse gas CO2, CO2 utilization is considered with much more promise as it could convert CO2 into value-added industrial products and achieve carbon cyclic utilization. Therefore, a high performance catalyst is supposed to be an important prerequisite to achieve CO2 activation and conversion. In this work, a new metal-free bifunctional porous organic framework (POF) heterogeneous catalyst, POF-PNA-Br–, has been successfully prepared with a two-step method. Because of the synergy of the carboxylic acid group as a Brønsted acidic site and the Br– anion generated from pyridine-based ionic liquids as the nucleophilic site, POF-PNA-Br– as a bifunctional metal-free environmentally friendly heterogeneous catalyst displayed an efficient catalytic performance for the cycloaddition reaction of CO2 and epoxide to form cyclic carbonate under mild and cocatalyst-free conditions. This work provides an efficient new method for the design and synthesis of bifunctional POF catalysts for the CO2 cycloaddition reaction.