Asymmetric Pore Windows in Pillar-Layered Metal-Organic Framework Membranes for H2/CO2 Separation

In this study, a novel ultramicroporous pillar-layered Ni-LAP-NH2 [Ni-2(l-asp)(2)(Pz-NH2)] (l-asp = l-aspartic acid, Pz-NH2 = aminopyrazine) membranes on porous alpha-Al2O3 tubes with high performance and good thermal stability was first fabricated using isostructural Ni-LAP[Ni-2(l-asp)(2)(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 -NH2 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 CO2 penetration. It was found that the preferential (111) orientation Ni-LAP-NH2 membrane (Z10) exhibited a high H-2/CO2 separation performance with a separation factor of 41.7 and H-2 permeance of 9.08 x 10(-8) mol<middle dot>m(-2)<middle dot>s(-1)<middle dot>Pa-1 under optimal conditions. These MOF materials demonstrated potential for industrial H-2 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.