High-Surface-Area Metalloporphyrin-Based Porous Ionic Polymers by the Direct Condensation Strategy for Enhanced CO2 Capture and Catalytic Conversion into Cyclic Carbonates.

Abstract

Metalloporphyrin-based porous organic polymers (POPs) that behave as advanced biomimetic nanoreactors have drawn continuous attention for heterogeneous CO2 catalysis in the past decades. Inspired by the double activation model of epoxides, the design and synthesis of metalloporphyrin-based porous ionic polymers (PIPs) are considered as one of the most promising approaches for converting CO2 to cyclic carbonates under cocatalyst- and solvent-free conditions. To overcome the obstacle of poor reaction activity of ionic monomers or highly irregular stacking architecture, in this paper, we have proposed and demonstrated a modular bottom-up approach for constructing a series of high-surface-area metalloporphyrin-based PIPs in high yields by the direct condensation strategy, thus boosting the close contact of multiple active sites and achieving the enhanced CO2 capture and catalytic conversion into cyclic carbonates with high turnover frequencies under mild conditions. These recyclable aluminum-porphyrin-based PIPs are featured with high surface areas, prominent CO2 adsorptive capacities, rigid porphyrin skeletons, and flexible ionic pendants, as well as the matched amounts and spatial positions of metal centers and ionic sites, in which is demonstrated to be one of the quite competitive catalysts. Therefore, this strategy of introducing ionic components into the porphyrin frameworks as flexible side chains rather than main chains and adjusting the reactivity ratios of comonomers by structure-oriented methods, provides feasible guidance for the multifunctionalization of metalloporphyrin-based POPs, thereby increasing the accessibility of multiple active sites and improving their synergistic catalytic behavior.