Thermodynamic-kinetic synergistic separation of CH4/N2 on a robust aluminum-based metal-organic framework

A robust aluminum-based metal–organic framework (Al-MOF) MIL-120Al with 1D rhombic ultra-microporous was reported. The nonpolar porous walls composed of para-benzene rings with a comparable pore size to the kinetic diameter of methane allow it to exhibit a novel thermodynamic-kinetic synergistic separation of CH 4 /N 2 mixtures. The CH 4 adsorption capacity was as high as 33.7 cm 3 /g (298 K, 1 bar), which is the highest uptake value among the Al-MOFs reported to date. The diffusion rates of CH 4 were faster than N 2 in this structure as confirmed by time-dependent kinetic adsorption profiles. Breakthrough experiments confirm that this MOF can completely separate the CH 4 /N 2 mixture and the separation performance is not affected in the presence of H 2 O. Theoretical calculations reveal that pore centers with more energetically-favorable binding sites for CH 4 than N 2 . The results of pressure swing adsorption (PSA) simulations indicate that MIL-120Al is a potential candidate for selective capture coal-mine methane.