Construction of hyper-crosslinked ionic polymers with high surface areas for effective CO2 capture and conversion

Abstract

The design and preparation of ionic liquids functionalized polymer materials is a trending topic in the fields of polymer science for CO2 capture and utilization. In this work, a series of porous hyper-crosslinked ionic polymers (PIPs) with high surface area and abundant catalytic central units have been synthesized by a simple post-crosslinking of ionic liquid monomer and 4,4′-bis(chloromethyl)-1,1′-biphenyl. The prepared PIPs were used for CO2 adsorption, and their adsorption capacity for CO2 exceeded 100 mg g−1 at 273 K and 1.0 bar. Furthermore, the isotherm adsorption data of CO2 were fitted respectively by Langmuir, Freundlich, Redlich-Peterson, and Toth isotherm models to calculate the thermodynamic parameters, including changes in Gibbs free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°), and isosteric heat of adsorption (ΔHIsosteric). It is concluded that the adsorption process of CO2 on PIP is a spontaneous physical process. These PIP can also be used as heterogeneous catalysts for the cycloaddition of CO2 with epoxides under metal/solvent/cocatalyst-free conditions. The excellent yields (up to 99%) of cyclic carbonates are ascribable to synergistic contributions of abundant microporous and active ionic catalytic centers. This study provides a new idea for developing functionalized ionic polymers that combine capture and conversion of CO2.