Developing mixed matrix membranes (MMMs) is challenging because the interface between different matrices often forms undesirable structures. Herein, we demonstrate a method of creating suitable CO2-selective channels based on interface regulation that greatly enhances membrane separation performance. The poly(vinylamine), which also acts as a polymer matrix, was immobilized onto covalent organic frameworks (COFs) to obtain polymer-COF hybrid materials (COFp). The COFp and polymer matrix are highly compatible because they have the same segment. The polymer matrix was induced to penetrate the oversized COFp, resulting in an amino-environmental pore wall and appropriately sized CO2-selective channels dispersed in MMMs. The MMMs exhibited satisfactory membrane performance for CO2/N2, CO2/CH4, and CO2/H2 separation. A CO2 transport model for preferential adsorption and transport is clearly presented for the first time. The membrane separation mechanism is also discussed. This work demonstrates potential applications for material, interface, and membrane investigations.
Keywords: CO2 separation; channel size; covalent organic frameworks; interface regulation; penetration.