Synthesis of Polycarbonates from CO2 Promoted by Immobilized Ionic Liquid Functionalized di-Mg Complex Catalyst

Abstract

The capture and conversion of anthropogenic CO2 is a paramount challenge for our global ecosystem. An optimal way of to cope with the emitted CO2 is to efficiently convert it to value-added materials. Whereas nature sequesters CO2 by making sugar-based polymers, utilizing CO2 to make highly demanded synthetic polymers such as polycarbonates is of great value. The present work reports the synthesis of a new supported ionic liquid (IL) functionalized organic ligand that is able to accept metal sites. After incorporating di-nuclear magnesium, it was utilized as a single-component solid catalyst for the copolymerization of CO2 and cyclohexene oxide. The obtained solid catalyst was found to be active under mild CO2 pressures of (1–15 atm) giving a turnover number of up to 283 and turnover frequency up to 11.8 h−1. To the authors knowledge, these rates are the highest obtained using a heterogeneous catalyst, maintaining 96–99 % polycarbonates selectivity and 97–99 % carbonate repeat units. In addition, the obtained polymers showed high molecular weights (16.7 to 11.7 kg/mol) with 1.05 to 1.6 dispersity (Đ). The catalyst was recycled 4 times, under regular laboratory conditions and without any intermediate reactivation steps, which provided ∼3 g of polycarbonate for ∼0.03 g catalyst (100 : 1) at 80 °C in neat cyclohexene oxide and 15 atm CO2.