Effective Separation of Acetylene/Ethylene by the Mesoporous MIL-100(Cr) MOF

Acetylene plays a key role in diverse commercial chemicals and high-quality fuel applications, yet its storage poses significant challenges due to its explosive nature. In-situ plasma-assisted CH₄ coupling conversion presents a promising alternative for the safe production of C₂ chemicals, including acetylene, assuming that efficient downstream separation processes are feasible. This study focuses on the adsorptive separation of acetylene from ethylene to achieve high-purity acetylene with the use of mesoporous metal-organic frameworks (MOFs) as effective selective adsorbents. Herein, we systematically investigate the acetylene/ethylene separation performance of a series of MIL-100 (M = Al, Fe, V, Cr) MOFs. Single-component sorption data first evidenced that MIL-100(Cr) shows the highest affinity to acetylene, supported by Operando Infrared spectroscopy and Density Functional Theory calculations. These analysis revealed the crucial role played by the Cr³⁺ coordinatively unsaturated sites and the counter-anions (OH^-/F^-) bound to 1 of the 3 Cr³⁺ atoms of the oxo-trimer. Grand Canonical Monte Carlo simulations further elucidated the microscopic adsorption mechanisms for each single-component and equimolar binary acetylene/ethylene mixtures. Breakthrough experiments demonstrated that MIL-100(Cr) achieves selectivity ranging from 5 to 23, suggesting its potential for dual high-purity acetylene and ethylene production. Vacuum Pressure Swing Adsorption (VPSA) cycle tests indicated that MIL-100(Cr) achieves high acetylene recovery and moderate purity without a rinse step, while an acetylene rinse step enhances purity for fine chemical raw materials. Overall, this study paves the way toward the promotion of MIL-100(Cr) for future large-scale industrial applications in acetylene harvesting and purification.