Work

Morphological engineering of hydrogen organic frameworks to boost CO2 separation in mixed matrix membranes

Year: 2025

Type: article

Abstract: Hydrogen-bonded organic frameworks (HOFs) have emerged as promising materials for membrane applications due to their well-defined porosity and solution processability. Nevertheless, HOF integration into mixed matrix membranes (MMMs) is constrained by the challenge of transforming bulky HOF particulate fillers into freestanding membranes with excellent polymer matrix compatibility. This study systematically synthesized HOF-ZJU-201 as the fillers in three distinct morphologies—nanocrystals (NC), nanosheets (NS), and nanopolyhedra (NP)—utilizing dimethylformamide as nucleation promoter and monocarboxylic acids (acetic acid/benzoic acid) as growth inhibitors. The morphology of the fillers significantly influenced gas separation performance, with NS-based PIM-1 MMMs showing the most pronounced enhancement. The optimized HOF-ZJU-201 NS/PIM-1 membrane with 5% HOFs achieved a CO2 permeability of 8738.4 Barrer and a CO2/N2 ideal selectivity of 31.2 in single-gas permeation tests, representing 99% higher permeability and 107% higher selectivity than pristine PIM-1 membrane. In mixed-gas tests, this membrane demonstrated CO2 permeability ranging from 7108.6 to 8419.6 Barrer and CO2/N2 selectivity of 43.7–50.2, outperforming many state-of-the-art MMMs. Mechanistic investigations revealed that the abundant -NH2 and -F functional groups formed polarized gas transport channels, enabling preferential CO2 permeation. Additionally, the horizontal arrangement of nanosheets, coupled with superior interfacial properties, markedly increased the diffusive resistance for N2 molecules. This research provides essential insights into HOF-based membranes and highlights morphological engineering as an effective strategy to optimize MMM performance for gas separation application.

Source: Journal of Membrane Science

DOI: 10.1016/j.memsci.2025.124636