Immobilization poly(ionic liquid)s into hierarchical porous covalent organic frameworks as heterogeneous catalyst for cycloaddition of CO2 with epoxides

The chemical fixation of CO2 into high value-added chemicals is of significant potential and sustainability to address the energy and ecological issues. To achieve great catalytic performance on the transformation of CO2, it is pivotal to strategically integrating several multifunctional and synergetic functionalities into the catalyst design and catalytic system construction. Herein, the poly(ionic liquid)-hierarchical porous covalent organic framework (PIL-HPCOF) hybrids were successfully synthesized via the formation of HPCOF through hard-template method, followed by in-situ polymerization of mono-vinyl decorated ionic liquids (ILs). The resultant PIL-HPCOF hybrids possess excellent versatility, with micropores providing high surface area to enhance CO2 uptake capacity and macropores supplying sufficient pore volume to promote mass transport of substrates. As a proof of concept, the conversion of CO2 with epoxides to produce cyclic carbonates was selected as a model reaction, which catalytic performance was obviously promoted by using PIL-HPCOF hybrids as the catalyst as compared to those of independent PIL and the PIL-COF hybrids with only micropores. Thus, it enables such a metal-free catalysis proceeds under much mild conditions (CO2 (1 MPa), 90 °C) and with broad substrates tolerance. These results supply the basis to design efficient and stable catalysts for CO2 conversion.