Polyamide membranes enabled by covalent organic framework nanofibers for efficient reverse osmosis

Polyamide reverse osmosis membranes are indispensable for the worldwide clean water supply. Incorporation of nanomaterials into polyamide separation layer provides an evident methodology to enhance the water flux. However, the desalination performance would be compromised by the inadequate compatibility between the nanomaterial and the polyamide matrix. In this work, we propose a straightforward strategy to use covalent organic frameworks (COF) nanofibers as the efficient nanofiller for the fabrication of high flux polyamide membranes. The COF nanofibers featuring crystalline structures, large surface area and well-defined micropores are synthesized by a surfactant-mediated solvothermal method. It is found that the COF nanofibers are able to mediate the interfacial polymerization process via the controlled release of amine molecules. This creates the reduced thickness of the polyamide separation layer. Moreover, the rigid and permanent nanopores of COF could serve as additional channels for water permeation. Benefitting from the low thickness and the additional channels, thus fabricated membranes exhibit a significantly enhanced water flux, while maintaining a slightly improved NaCl rejection. Our work is expected to provide a new insight for the design and fabrication of advanced polyamide reverse osmosis membranes.