Boosting C2H2/CO2 separation by porous organic cages through the amino-functionalization of cavities

Abstract

The in-depth investigation of the structure–property relationship in porous organic cages (POCs) for real gas mixture separation is both significant and challenging. In this work, we employed microenvironment modulation strategy to systematically regulate the gas adsorption and separation performance of POCs. The introduction of amino groups into the cavity of [2 + 4] lantern-shaped POC (CPOC-108) can effectively facilitate multiple host–guest interactions in confined cavities via forming hydrogen bond interactions. The as-prepared amino-functionalized POC (CPOC-108-NH2) thus exhibits remarkably enhanced C2H2 and CO2 adsorption capacities, especially for the more polarizable C2H2 gas, as well as higher C2H2/CO2 selectivity in comparison to CPOC-108. More importantly, CPOC-108-NH2 displays significantly improved separation performance for C2H2/CO2 mixture, as evidenced by dynamic breakthrough experiments. This work provides an elegant example for a comparative study on C2H2/CO2 separation properties between amino-functionalized and unsubstituted POCs, and may shed light on fine-tuning the cavity surfaces of POCs to rationally regulate their properties.