Achieving Molecular Sieving of CO₂ from CH₄ by Controlled Dynamical Movement and Host-Guest Interactions in Ultramicroporous VOFFIVE-1-Ni by Pillar Substitution.

Abstract

Engineering the building blocks in metal-organic materials is an effective strategy for tuning their dynamical properties and can affect their response to external guest molecules. Tailoring the interaction and diffusion of molecules into these structures is highly important, particularly for applications related to gas separation. Herein, we report a vanadium-based hybrid ultramicroporous material, VOFFIVE-1-Ni, with temperature-dependent dynamical properties and a strong affinity to effectively capture and separate carbon dioxide (CO₂) from methane (CH₄). VOFFIVE-1-Ni exhibits a CO₂ uptake of 12.08 wt % (2.75 mmol g^-1), a negligible CH₄ uptake at 293 K (0.5 bar), and an excellent CO₂-over-CH₄ uptake ratio of 2280, far exceeding that of similar materials. The material also exhibits a favorable CO₂ enthalpy of adsorption below -50 kJ mol^-1, as well as fast CO₂ adsorption rates (90% uptake reached within 20 s) that render the hydrolytically stable VOFFIVE-1-Ni a promising sorbent for applications such as biogas upgrading.