Brij Mohan, Virender Virender, Harish Kumar Sharma, Sandeep Kumar, Ajeet Singh, Armando J.L. Pombeiro, Rakesh Kumar Gupta*, Gurjaspreet Singh*, Wei Sun*

Cite this article: https://doi.org/10.1016/j.cjsc.2026.100982

Publication date:

Keywords: Metal-organic frameworks; Breathing; Structural flexibility; Surface area; Gas and liquid separation

ABSTRACT

Flexible metal–organic frameworks (MOFs) are revolutionizing separation science by offering tunable selectivity based on structural dynamics, unlike traditional rigid adsorbents. These materials respond to stimuli such as pressure, adsorption, and temperature through gate opening, breathing, and swelling, allowing dynamic pore reconfiguration. This review links these structural transitions to separation performance in gas and liquid systems, categorizing behavior by thermodynamics and kinetics. These responsive changes produce pressure-dependent selectivity, stepwise isotherms, and inversion, phenomena impossible with conventional porous materials. This review discusses the impact of framework flexibility on mixed-component separations, focusing on transition kinetics, hysteresis, and stability. Despite the promise, challenges like slow rates, fatigue, and response variability hinder industrial use. Insights from molecular design, thermodynamics, and engineering guide tuning gate pressures, transition pathways, and selectivity. We highlight future research directions and scale-up opportunities for practical separation technologies.