Simultaneous surface and pore structure modification for growth of ZIF-8 membranes on coarse macroporous tube

Here we report a modified "two in one" strategy through depositing of ZnO particles onto the macroporous alpha-alumina tubes with average pore size of 2-3 mu m for synthesis of ZIF-8 membranes. The LTA or Al2O3 particles as fillers were firstly deposited to patch the large defects in the support then the ZnO particles were deposited. The ZnO particles reduce the pore size and simultaneously act as "metal source" to create a high supersaturation degree to promote high heterogeneous nucleation sites. Through such strategy, continuous and crack-free ZIF-8 membranes were successfully obtained, exhibiting H-2 permeance of 3.4 x 10(-7) mol m(-2) s(-1) Pa-1 at 150 degrees C, with ideal selectivities for H-2/CO2, H-2/N-2, H-2/CH4 and H-2/C3H8 system of 7.4, 8.8, 8.2 and 37.8, respectively. When the supports deposited with ZnO particles were treated by pre-reacting with the ligand of 2-methylimidazole, big cracks/gaps occurred at the interface between the ZIF-8 membranes and the supports. This modified "two in one" strategy can be extended for synthesis of large variety of MOFs membranes on large-pore supports through the rational selection of metal oxides. (C) 2014 Elsevier Inc. All rights reserved.