A MOF membrane with ultrathin ZIF-8 layer bonded on ZIF-8 in-situ embedded PSf substrate

Metal–organic framework (MOF) membranes exhibit enormous potential for molecular mixtures’ sieving with high permeance, as well as high selectivity. Current MOF composite membranes suffer from unduly thick MOF layer and poor adhesion to the porous support. By a simple multiple seeded growth method, the ultrathin (less than 200 nm) and defect-free MOF layer is prepared on a ZIF-8 in-situ embedded PSf substrate. On the one hand, the nano-sized ZIF-8 crystals embedded on substrate surface act as anchors linking the ZIF-8 layer with the substrate. On the other hand, these ZIF-8 crystals also act as seeds to promote the formation of the ZIF-8 layer and reduce the crystallization time, leading to a thin and continuous ZIF-8 layer. The obtained ultrathin ZIF-8 membrane shows superior gas molecular sieving performance, with a high gas permeance of 24.5 × 10−7 mol/m2/s/Pa for H2 and selectivity of 4.5, 23.2, and 31.5 for H2/CO2, H2/N2, and H2/CH4, respectively. In addition, neither the permeance or the selectivity shows a noticeable change after 3% elongation, which indicates high mechanical integrity of the MOF layer on the ZIF-8 in-situ embedded PSf substrate. We believe that the utilization of MOF in-situ embedded polymer substrate offers a universal and simple strategy strengthening and thinning the MOF layer of its composite membranes.