Boosting CO₂ Catalytic Fixation to Cyclic Carbonates over Aluminum Porphyrin-Based Porous Hyper-Cross-Linked Ionic Polymers via Synthetic Control of Active Site Proximity

Multifunctionalization of porous organic polymers (POPs) toward cooperative CO₂ catalysis has attracted so much attention in recent years, but it still remains a huge challenge to scientists. In this contribution, a concise and efficient method to construct aluminum porphyrin-based hyper-cross-linked ionic polymers has been demonstrated for the first time, which are featured with high surface areas and hierarchical structures. Obviously, the preparation of metalloporphyrin-based hyper-cross-linked polymers with tetraphenylmethane-derived three-dimensional structures is beneficial for the introduction of abundant ionic active sites and the formation of hierarchical porous structures. By regulating the locations and amounts of cooperative active sites to make them highly dispersed and easily accessible, the catalytic activity of as-maded catalyst can be greatly improved for CO₂ cycloaddition conversion to cyclic carbonates without cocatalysts and solvents, providing the highest initial turnover frequency up to 8400 h^-1 of heterogeneous catalysts reported to date. In addition, the catalyst can be easily recovered by filtration and reused at least ten times without a significant decrease in catalytic activity. This work not only presents a promising strategy to improve the catalytic activity by controlling active site proximity via different synthetic methods but also offers an attractive perspective in the field of CO₂ catalytic conversion.