An innovative approach for the preparation of confined ZIF-8 membranes by conversion of ZnO ALD layers

An innovative eco-friendly approach has been developed for the synthesis of ZIF-8-based nanocomposite membranes. The method involves the Atomic Layer Deposition (ALD) of ZnO thin films on the grains of a macroporous ceramic support and their subsequent conversion to ZIF-8 using a 2-methylimidazole/methanol solution under solvothermal conditions. Despite applying extremely low quantity of chemicals, reproducible and good quality ZIF-8-based membranes have been obtained, in which the ZIF-8 material was fully confined within the ceramic support macropores, thus leading to enhanced thermo-mechanical strength. A judicious choice of both the deposition conditions of ZnO layers and the solvothermal treatment parameters for their subsequent conversion to ZIF-8 was the key point for validation of this original protocol and evaluation of its potential for up scaling on tubular industrial supports. The physico-chemical characterization of the ZIF-8/ZnO/alpha-Al2O3 nanocomposite membranes was completed by a study of their gas transport properties. Reproducible ZIF-8/ZnO/alpha-Al2O3 nanocomposite membranes were produced and tested in the separation of binary gas mixtures: membranes were found to extract H-2 from H-2/CO2 and H-2/CH4 equimolar gas mixtures with selectivities of about 7.8 and 12.5 respectively, measured at 100 degrees C. (C) 2014 Elsevier B.V. All rights reserved.