Nano-array assisted metal-organic polyhedra membranes for the pervaporation of aromatic/aliphatic mixtures

Metal-organic polyhedra (MOP), as a new type of molecule-based porous nanocage, is a promising material in membrane separation. However, it is a challenge to obtain pure MOP membrane to take full advantage of its nanocage. In this study, [Cu-24(5-tBu-1,3-BDC)(24)(S)(24)] (MOP-tBu) membranes were prepared on the surface of ceramic tubular substrate with the assistance of Co(OH)(2) nano-array. MOP-tBu molecules were dynamic pressure- driven assembled into the confinement space of vertically arranged Co(OH)(2) nanosheets, which were previously formed on the substrate through hydrothermal synthesis. With this strategy, the MOP-tBu molecules can form an ultrathin defect-free separation layer on the surface of the substrate. Due to the open Cu2+ unsaturated sites (CUSs) and rich benzene rings in its structure, the MOP-tBu membrane has permselectivity towards the aromatic compounds. In addition, the MOP-tBu membrane is endowed with high permeability because of its large cavity and small apertures. Therefore, the membranes were used to separate aromatic/aliphatic mixtures through pervaporation. When separating 50 wt% toluene/n-heptane mixtures, the permeate flux of the MOP-tBu membrane was 800 gm(-2) h(-1) with the separation factor of 5.4. The high permeability of the membrane exhibited great potential in the separation of aromatic/aliphatic mixtures.