Interfacial growth strategy for synthesizing Mg-MOF-74@clinoptilolites with hierarchical structures for enhancing adsorptive separation performance of CO2/CH4, CH4/N2 and CO2/N2

The purification and separation of CO₂, CH₄, and N₂ from biogas, flue gas, and coalbed gas for carbon capture and storage are main technology in mitigating the greenhouse effect. The Mg-MOF-74@clinoptilolite (Mg-MOF-74@CP) composites are successfully synthesized through an interfacial growth of Mg-MOF-74 onto the surfaces of the synthesized CP for adsorption and separation of CO₂, CH₄, and N₂. The structural characteristics of the resultant composites are systematically characterized by various characterizations. In particular, small-angle X-ray scattering (SAXS) patterns are used to elucidate the fractal structural evolutions of the parent CP, Mg-MOF-74, and Mg-MOF-74@CP. Meanwhile, the single-component adsorption isotherms for CO₂, CH₄, and N₂ are demonstrated. The breakthrough measurements on CO₂/CH₄ and cycling tests on CO₂ are conducted. The results elucidate that the CO₂ equilibrium capacity of Mg-MOF-74@CP is higher than that of parent CP, displaying a high affinity toward CO₂, the longer breakthrough time and enhancement of CO₂ uptake exhibit a better separation performance. The cycling tests on CO₂ reveal that the Mg-MOF-74@CP could be used repetitively, promoting its practical application in an energy-saving and economical way. Additionally, the adsorption isotherms and adsorption sites of the prepared Mg-MOF-74@CP are simulated using the Grand Canonical Monte Carlo (GCMC) method, elucidating the mechanism of the gas separation performance of Mg-MOF-74@CP.