Directional anchoring of cobalt metal sites in mixed matrix membranes via interfacial covalent grafting for synchronous separation of particulate matter and CO2

Abstract

In the co-capture technology for particulate matter (PM) and carbon dioxide (CO₂) using mixed matrix membranes (MMMs), concentration polarization at the membrane surface, along with the inappropriate selection and proportion of active layer and substrate, are primary factors influencing both separation efficiency and production performance. However, the fabrication of defect-free solid-gas separation membranes with enhanced permeability selectivity and phase compatibility remains a challenge due to the formation of substrate-filler interface defects and filler aggregation. In this study, the use of cobalt-coordinated conjugated microporous polymers (CMPs) as an adsorptive active layer for interfacial modification effectively mitigates the aggregation of porous fillers and enhances the interaction between the substrate and filler components, thereby forming MMMs with superior interfacial compatibility and selectivity towards harmful PM and mixed gas components. The Co-CMP-MWCNTs exhibited a capture efficiency for PM_3.0 exceeding 99.9 % in acidic and alkaline environments, with a high ideal adsorption solution theory (IAST) selectivity of 160 for CO₂/N₂ mixed components. By comparing the experimental data with the calculations of density functional theory (DFT), the structure-activity relationship between the precise control of pore size and the interaction of active sites with guest molecules and the enhancement of membrane permeation selectivity was elucidated. Based on the structural regulation and polymerization optimization of porous fillers, by reducing particle agglomeration and improving the substrate-filler compatibility, the CMPs-based membranes can adjust the inherent trade-off between selectivity and permeability in the solid-gas mixed separation system, providing a theoretical basis for the precise design and rational creation of high-value-added membranes.