Agile construction of bifunctional bipyridine-based hyper-cross-linked ionic polymers for efficient CO2 adsorption and conversion

Porous organic polymers (POPs) are a very promising CO2 adsorption material due to their well-developed pore structure and high specific surface area, but they generally have no catalytic activity for cycloaddition of CO2 and epoxides. Introducing ionic sites into the polymer backbone can endow POPs with unique properties such as both adsorption and catalytic conversion of CO2. In this work, several novel bipyridine-based hyper-cross-linked ionic polymers (HCIPs) were fabricated by using a one-pot method with simultaneous quaternization and Friedel-Crafts reactions, and HCIPs with hierarchical pore structure and high specific surface area (up to 1448 m2·g−1) are acquired by adjusting the structure of polymerized monomers. The plentiful micro-mesoporous and indigenous ion pair active centers of the as-prepared HCIPs are conducive to the adsorption and conversion of CO2. The results showed that these bipyridine-based HCIPs can not only effectively adsorb CO2, but also serve as the metal-free catalysts for cycloaddition of CO2 with epoxides, affording the highest CO2 uptake of 2.75 mmol·g−1 at 0 °C and 1.0 bar and moderate to good yields of cyclic carbonates. This study provides a feasible strategy for the design and synthesis of structurally controllable HCIPs for adsorption and conversion of CO2.