Gas Mixture Diffusion and Distribution in the Porous ZIF-90 Framework

Abstract

Understanding how gas mixtures diffuse and distribute within porous frameworks is central to designing advanced separation and storage materials. Here, we investigate the transport and spatial distribution of binary gas mixtures in a porous metal organic framework, viz., ZIF-90, using molecular simulations. We perform grand canonical Monte Carlo (GCMC) simulations to examine the competitive adsorption of carbon dioxide and nitrogen from a binary gas mixture in ZIF-90, while molecular dynamics (MD) simulations are conducted to investigate the transport behavior of the adsorbed molecules within the framework. These integrated simulations reveal that the framework topology and pore chemistry jointly dictate diffusion pathways and preferential occupancy of gas species, underscoring their intrinsic interdependence. Competitive adsorption leads to distinct spatial partitioning within the pores, which in turn modulates mixture diffusivity inside the porous medium compared to their bulk properties. Our results provide molecular-level insight into how ZIF-90 accommodates and separates gas mixtures, offering design principles for optimizing metal-organic frameworks in energy and environmental applications.