Precise modulation of MOF pore structures via functional group dimensions and spatial configuration for membrane separation

Abstract

Traditional petroleum distillation faces high energy demands, necessitating innovative alternatives like membrane separation. This study presents a breakthrough in dual-range and precise pore size modulation of metal-organic frameworks (MOFs) through a ligand functionalization strategy. By tailoring steric configurations and spatial orientations of light-responsive azobenzene groups, we achieved broad-range pore tuning (0.41 to 0.68 nanometers) via functional group length variation, coupled with subnanometer precision through reversible trans-to-cis photoisomerization. Four representative branched alkanes were selected to validate the MOF’s high selectivity. Results showed its capacity to generate a constant carbon-atom-count–dependent permeation gradient, realizing a four-step sequential separation that increased C 6 H 14 purity from 25 to 92.2%. This synergistic approach uniquely combines large-scale pore adjustment with dynamic fine-tuning, decoupling separation efficiency from energy-intensive processes. The membranes’ structural stability and reversible light responsiveness further highlight their potential for sustainable hydrocarbon processing. By integrating molecular design with stimuli-responsive control, this work advances MOF-based membranes as a transformative solution for energy-efficient petroleum fractionation and precise molecular sieving. MOF membranes can achieve pore structure and aperture regulation via functional group-light modulation for alkane separation.