Abstract
A robust aluminum-based metal-organic framework (Al-MOF) MIL-120Al with
1D rhombic ultra-microporous was reported. The non-polar 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
CH4/N2 mixtures. The CH4adsorption capacity was as high as 33.7 cm3/g (298 K,
1 bar), which is the highest uptake value among the Al-MOFs reported to
date. The diffusion rates of CH4 were faster than
N2 in this structure as confirmed by time-dependent
kinetic adsorption profiles. Breakthrough experiments confirm that this
MOF can completely separate the CH4/N2mixture and the separation performance is not affected in the presence
of H2O. Theoretical calculations reveal that pore
centers with more energetically-favorable binding sites for
CH4 than N2. The results of pressure
swing adsorption (PSA) simulations indicate that MIL-120Al is a
potential candidate for selective capture coal-mine methane.