Thin-film nanocomposite membrane doped with carboxylated covalent organic frameworks for efficient forward osmosis desalination

Compared to the inorganic nanofillers, an organic one might be more appropriate to control the aggregation and interfacial microvoids between nanofiller and polymeric matrix for an efficient mixed matrix membrane. In this study, a hydrophilic carboxylated covalent organic frameworks (COF-COOH) as an organic nanofiller, for the first time, was conveniently incorporated to fabricate a novel thin-film nanocomposite (TFN) membrane via interfacial polymerization. Thanks to the abundant carboxyl groups and pure organic nature of COF-COOH, the TFN membrane was endowed with an improved hydrophilicity and negative charge property. With COF-COOH content of 0.5 mg ml(-1) in aqueous solution, the elaborately designed TFN membrane rendered a smaller mean pore size of 0.45 nm and an ultralow structural parameter of 58.6 mu m, exhibiting a 4-fold water flux (J(v)) of 64.2 L m(-2) h(-1) with a synchronously improved selectivity (J(v)/J(s) as high as 10.0 L g(-1)), compared to a pristine TFC membrane (Jv = 15.9 L m(-2) h(-1), J(v)/J(s) = 2.6 L g(-1)) in forward osmosis (FO) mode with 1 mol L-1 NaCl as draw solution and DI water as feed solution. The intriguing results shed light on the potential of COFs in the highly efficient membranes for water desalination and purification.