Engineering HOF-Based Mixed-Matrix Membranes for Efficient CO2 Separation

Hydrogen-bonded organic frameworks (HOFs) have emerged as a new class of crystalline porous materials, and their application in membrane technology needs to be explored. Herein, for the first time, we demonstrated the utilization of HOF-based mixed-matrix membrane for CO₂ separation. HOF-21, a unique metallo-hydrogen-bonded organic framework material, was designed and processed into nanofillers via amine modulator, uniformly dispersing with Pebax polymer. Featured with the mix-bonded framework, HOF-21 possessed moderate pore size of 0.35 nm and displayed excellent stability under humid feed gas. The chemical functions of multiple binding sites and continuous hydrogen-bonded network jointly facilitated the mass transport of CO₂. The resulting HOF-21 mixed-matrix membrane exhibited a permeability above 750 Barrer, a selectivity of ~ 40 for CO₂/CH₄ and ~ 60 for CO₂/N₂, surpassing the 2008 Robeson upper bound. This work enlarges the family of mixed-matrix membranes and lays the foundation for HOF membrane development.