Anionic Ni-Based Metal-Organic Framework with Li(I) Cations in the Pores for Efficient C₂H₂/CO₂ Separation

Acetylene (C₂H₂) is widely used as a raw material for producing various downstream commodities in the petrochemical and electronic industry. Therefore, the acquisition of high-purity C₂H₂ from a C₂H₂/CO₂ mixture produced by partial methane combustion or thermal hydrocarbon cracking is of great significance yet highly challenging due to their similar physical and chemical properties. Herein, we report an anionic metal-organic framework (MOF) named LIFM-210, which has Li⁺ cations in the pores and shows a higher adsorption affinity for C₂H₂ than CO₂. LIFM-210 is constructed by a unique tetranuclear Ni(II) cluster acting as a 10-connected node and an organic ligand acting as a 5-connected node. Single-component adsorption and transient breakthrough experiments demonstrate the good C₂H₂ selective separation performance of LIFM-210. Theoretical calculations revealed that Li⁺ ions strongly prefer C₂H₂ to CO₂ and are primary adsorption sites, playing vital roles in the selective separation of C₂H₂/CO₂.