Plasma-assisted synthesis of ZIF-8 membrane for hydrogen separation

Well-intergrown MOF membranes were challenging to construct using the in-situ approach, due to the poor heterogeneous nucleation of MOF on the supports. Here, we described a technique to manufacture ZIF-8 membranes devoid of induced seeds using support modified by O2 plasma for the first time. O2 plasma can increase the number of oxygen-containing functional groups (–OH) on the support surface that could absorb zinc ions from synthesizing solution and offer heterogeneous nucleation sites for the formation of ZIF-8 membranes. The as-synthesized membrane exhibits outstanding gas permeation performance with a high hydrogen permeance of about 2.22 × 10−7 mol·m−2·s−1·Pa−1 and a high H2/CH4 ideal selectivity of 25.91. The separation factor of the equimolar H2/CO2 and H2/CH4 mixtures reached 8.72 and 31.03 at 298 K and 0.1 MPa, respectively. In addition, this new technique also allowed for the synthesis of ZIF-67 membranes, and the prepared membrane had an H2/CH4 ideal selectivity of 14.92. This work develops a new route for the efficient fabrication of MOF membranes.