A well inter-grown ZIF-8 membrane synthesized via two-step hydrothermal synthesis on coarse α-Al2O3 support

•A well intergrown ZIF-8 membrane synthesized via two-step hydrothermal synthesis.•CO2/N2 and CO2/CH4 gas separations were performed on the ZIF-8 membrane.•CO2/N2 and CO2/CH4 separations showed significant selectivities of 3.4 and 4.0.

Here, we report the fabrication of a well inter-grown ZIF-8 membrane on coarse α-Al2O3 support via a two-step hydrothermal synthesis method. The ZIF-8 seeds were initially vacuum seeded to ensure overall coverage of the voids on the α-Al2O3 support followed by hydrothermally treated twice for forming well inter-grown membrane. The presence of sodium formate was found to be of critical importance to enable the growth of ZIF-8 structure into a continuous membrane. This method enabled our ZIF-8 membrane to exhibit CO2 permeance of 3.49×10−7 mol/m2 s Pa with significant CO2/N2 and CO2/CH4 selectivity of 3.4 and 4.0, respectively.