Asymmetric Pore Windows in Pillar-Layered Metal-Organic Framework Membranes for H/CO Separation.

In this study, a novel ultramicroporous pillar-layered Ni-LAP-NH [Ni(l-asp)(Pz-NH)] (l-asp = l-aspartic acid, Pz-NH = aminopyrazine) membranes on porous α-AlO tubes with high performance and good thermal stability was first fabricated using isostructural Ni-LAP[Ni(l-asp)(Pz)] (Pz = pyrazine) crystals as seeds. Utilizing the principle of reticular chemistry, here, we introduced the active amino side group into the Ni-LAP frameworks by replacing the pillar-layered ligand Pz with Pz -NH while maintaining the original Ni-LAP small pore size, and the amino side group induced a "steric hindrance" effect and the physical adsorption affinity, which synergistically delayed CO penetration. It was found that the preferential (111) orientation Ni-LAP-NH membrane (Z10) exhibited a high H/CO separation performance with a separation factor of 41.7 and H permeance of 9.08 × 10 mol·m·s·Pa under optimal conditions. These MOF materials demonstrated potential for industrial H purification due to their tunable pore structure and remarkable stability. Moreover, this strategy offers an effective approach to tailoring pillar-layered MOF membranes with targeted molecular sieving ability.