A Thermally Rearranged\nPoly(benzoxazole) Composite\nMembrane for Gas Separation Prepared by Vapor Phase Growth

Compositing metal organic framework (MOF) powder with\na polymer\nsubstrate is an effective way to obtain an efficient gas separation\nmembrane. However, the weak polymer–filler interaction usually\nleads to the formation of nonselective cracks in the composite material.\nHere, we report a MOF–polymer composite membrane with a continuous\nand dense MOF layer, which was synthesized by magnetron sputtering\nand vapor phase growth. A thermally rearranged poly(benzoxazole) (TR-PBO)\nmembrane was converted from a hydroxy-polyimide precursor by a thermal\nrearrangement reaction, which was used as the polymer support of the\ncomposite membrane. An ultrathin ZnO seed layer was deposited on the\nTR-PBO support by magnetron sputtering technology, and then it was\nconverted to a ZIF-8 layer by vapor phase growth. Scanning electron\nmicroscopy results confirm the formation of a dense, flat, and continuous\nZIF layer with a thickness of about 450–600 nm. The ZIF-8 nanoparticles\nare uniform in size and evenly distributed. Furthermore, the attached\nZIF layer significantly improves the gas selectivity of the composite\nmembrane, which should be attributed to the sieving effect of the\nunique pore structure of ZIF-8. The method of magnetron sputtering\ncombined with vapor phase growth is effective for improving the selectivity\nof the gas separation membrane and reducing the aggregation of MOF\nparticles, which opens up a way for the design of flat and ultrathin\ngas separation composite membranes.