Ultramicroporous Organophosphorus Polymers via Self-Accelerating P-C Coupling Reactions: Kinetic Effects on Crosslinking Environments and Porous Structures.

Abstract

Porous organic polymers (POPs) have drawn significant attention in diverse applications. However, factors affecting the heterogeneous polymerization and porosity of POPs are still not well understood. Herein, we report a new strategy to construct porous organophosphorus polymers (POPPs) with high surface areas (1283 m2/g) and ultramicroporous structures (0.67 nm). The strategy harnesses an efficient transition-metal-catalyzed phosphorus-carbon (P-C) coupling reaction at the trigonal pyramidal P-center, which is distinct from the typical carbon-carbon coupling reaction utilized in the synthesis of POPs. As the first kinetic study on the coupling reaction of POPs, we uncovered a self-accelerating reaction characteristic, which is controlled by the choice of bases and catalysts. The self-accelerating characteristic of the P-C coupling reaction is beneficial for the high surface area and uniform ultramicroporosity of POPPs. The direct crosslinking of the P-centers allows 31P solid-state (ss)NMR experiments to unambiguously reveal the crosslinking environments of POPPs. Leveraging on the kinetic studies and 31P ssNMR studies, we were able to reveal the kinetic effects of the P-C coupling reaction on both the crosslinking environments and the porous structures of POPPs. Furthermore, our studies show that the CO2 uptake capacity of POPPs is highly dependent on their porous structures. Overall, our studies paves the way to design new POPs with better controlled chemical and ultramicroporous structures, which have potential applications for CO2 capture and separation.