Construction of π-Complexation Sites in Metal–Organic Framework for Efficient Natural Gas Purification with C ₂ H ₂ /CH ₄ /CO ₂ Separations

The efficient separation of methane, the primary component of natural gas, from gas mixtures remains a critical challenge in industrial processes. Due to the adjustable pore size and structural designability of metal–organic framework (MOF) materials, developing new adsorbents for C2H2/CH4 and CO2/CH4 mixed systems is a research focus. In this work, a Cd-based MOF (Cd-TPCA) with ssb topology was constructed using tetracarboxylic acid ligand H4TPCA, followed by postsynthetic modification to introduce Cu metal sites, yielding functionalized Cu@Cd-TPCA. Experimental results demonstrated that Cu@Cd-TPCA exhibited superior adsorption capacities for C2H2 (46 cm3 g–1) and CO2 (28 cm3 g–1) over CH4 (9 cm3 g–1) at 298 K and 1 atom. Ideal adsorbed solution theory (IAST) calculations revealed high selectivity coefficients of 26.4 for equimolar C2H2/CH4 and 4.4 for CO2/CH4 mixtures. Remarkably, the material maintained robust chemical stability and cycling performance, underscoring its potential for industrial implementation in the C2H2/CH4 and CO2/CH4 separation processes.