Coaxially covalent grafted strategy for core–shell structured CMP-CNTs hybrid membranes to enhance permeability and selectivity

Abstract

The utilization of Mixed Matrix Membranes (MMMs) has been extensively employed to enhance the adsorption and separation performance by integrating the advantageous properties of polymers with organic/inorganic fillers. Conjugated microporous polymers (CMPs), distinguished by their hierarchical porous structure and abundant heteroatom adsorption sites, enable efficient and robust gas adsorption and separation in intricate surroundings. We proposed the concept of constructing a carbon nanotube (CNTs) network-supported CMPs membrane, which consists of CNTs with a three-dimensional network structure as the core and CMPs with a hierarchical pore structure and abundant heteroatom adsorption sites as the shell, aiming to address the challenging issue of membrane formation during the preparation process. The CMP-CNTs membrane prepared retain the three-dimensional network structure of CNTs and the hierarchical porous structure of CMPs, resulting in a significant reduction in permeation resistance while ensuring efficient adsorption and separation of particulate matter (PM) as well as carbon dioxide/nitrogen (CO2/N2). CMP-CNTs have an interception efficiency of over 99.9 % for PM3.0 in acid-base environments. The ESP calculations reveal that the pore characteristics similar to the gas molecule kinetic diameters and the polarity-induced environment by nitrogen and oxygen heteroatoms bestow CMP-CNTs with exceptional CO2/N2 separation capabilities. CMP-CNTs exhibit an impressive IAST selectivity of up to 123 for the mixed CO2/N2 fractions (at 273 K and 1.0 bar). We proposed organic/inorganic hybrid membranes with core–shell structure formed by coaxial covalent grafting of CMPs on the surface of CNTs, this processing method with complementary advantages of organic/inorganic materials has design flexibility and process universality.