Mixed matrix membranes containing exceptional Bi-HHTP MOF for highly-efficient CO2/N2 separation

Constructing high-performance mixed matrix membranes (MMMs) with highly permeable polymers of intrinsic microporosity (PIMs) and metal-organic frameworks (MOFs) faces critical challenge of poor interfacial compatibility between MOF fillers and the polymer matrix and difficulty in maintaining a defect-free interface at high filler loading (over 30 %). In this study, a Bi-HHTP loading as high as 50 wt% and uniform dispersion with excellent interfacial integrity is achieved in our high-performance MMMs through the elaborate design of multiple synergistic interfacial interactions, including hydrogen bonding between the phenolic hydroxyl groups of the 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) ligand in the Bi-HHTP filler and the cyano groups in the PIM-1 matrix and π-π stacking between their benzene ring structures. The optimized MMM exhibits a remarkable CO 2 permeability up to 4021 Barrer with an ideal CO 2 /N 2 selectivity of 42.1 which substantially outperforms the neat PIM-1 membrane and exceeds the 2019 upper bound. The enhanced separation performance of the MMMs stems mainly from the significant increase in CO 2 solubility selectivity with Bi-HHTP loading, which benefits from the inherent CO 2 affinity of Bi-HHTP and the effective suppression of N 2 dissolution by the rigidification of PIM-1 chain segments induced by strong interfacial interactions. Most importantly, the resulted high-loading MMMs exhibited remarkable structural stability, showing strong resistance to both physical aging and CO 2 -induced plasticization. This strategy overcomes the loading bottlenecks of state-of-the-art MMMs and contributes advanced membrane materials for efficient CO 2 capture.