Photochargeable Nanopores in Gas Permselective Membrane.

Abstract

Gas permselective membranes are inherently constrained by a trade-off between permeability and selectivity. Overcoming this limitation is key to enabling broader industrial adoption, and advanced porous materials-particularly metal-organic framework (MOF)-has emerged as promising candidate. Yet, to truly rival established separation technologies such as, distillation, pressure swing adsorption and chemisorption, innovative design strategies remain essential. Traditionally, efforts to surpass the trade-off have focused on regulating porosity, pore architecture, pore surface chemical functionality, and macroscopic transport pathways (particle morphology). These modifications are achieved either through bottom-up synthetic approaches or by employing external stimuli such as light, pressure, or electric fields. In this work, we introduce a photochargeable membrane that enhances gas permselectivity through precise, molecule-specific interactions-without altering the underlying porous architecture. This is achieved by incorporating a nanoporous MOF, constructed from redox-active organic ligands, as filler in a mixed matrix membrane. Upon photoexcitation, ligand-ligand charge separation yields stable pore surface charges, facilitating selective interactions with quadrupolar CO₂. This specific interaction enhances CO₂/N₂ and CO₂/CH₄ permselectivity, surpassing the Robeson upper bound. The proof-of-concept can be explored for mixed and high purity gas feed preparation.