Fabrication of defect-free thin-film nanocomposite (TFN) membranes for reverse osmosis desalination

The rise of porous nanomaterials has stimulated a new research thrust on novel thin-film nanocomposite (TFN) reverse osmosis (RO) membranes. While encouraging results of greater permeability have been reported, they are usually companied by an inferior membrane selectivity due to the agglomeration of nanomaterials and low compatibility between the nanomaterials and polyamide matrix. Herein, to sustain the membrane selectivity at the molecular level, a type of metal-organic frameworks (MOFs), namely UiO-66-NH2 nanoparticles, have been modified with different amount of tannic acid (TA) before participating in interfacial polymerization. Due to the inherent porous nature and improved hydrophilicity of the modified MOFs, the resultant TFN membranes (referred to as TFN-TU) show a remarkable increase in water permeance compared to both conventional thin-film composite (TFC) and UiO-66-NH2 incorporated membranes (TFN-U). Thanks to the bridging effects of TA, TFN-TU membranes exhibit a higher salt rejection than TFN-U membranes for brackish water desalination. In addition, for seawater desalination, TFN-TU membranes possess a higher water flux as well as a higher salt rejection than the TFC membranes. This work may offer insights and strategies for the development of advanced TFN membranes for desalination with a high water product quality.