Unravelling the functional role of two-dimensional metal organic framework interlayer for boosted nanofiltration performance

Tailor-made highly permeable and selective polyamide (PA) nanofiltration (NF) membranes are imperative for diverse aqueous applications such as seawater desalination, brine softening and wastewater treatment. Here we report a high-performance PA NF membrane having a 2D MIL-100 (Fe) nanoflakes intermediate layer with tortuous mass transfer channels and dense PA barrier layer with ultrathin thickness (25.7 nm) and wrinkled structure. The MIL-100 (Fe) nanosheets interlayer was deposited onto the support and then the interfacial polymerization (IP) reaction occurred on MIL-100 (Fe) interlayer. The MIL-100 (Fe) nanosheets interlayer affected the IP reaction by influencing the diamine monomers storage and diffusion behavior during IP procedure. By only altering the MIL-100 (Fe) nanosheets deposition amounts and monomers concentrations for IP, a series of PA nanofilms with governable membranes structures and crosslinking degree could be formed. The best-performing TFC NF membrane (PA_MIL_1.0) with improved separation performance demonstrated fascinating water permeance of 16.1 L m −2  h −1 bar −1 with greater salts selectivity (99.1 % and 97.8 % for Na 2 SO 4 and MgSO 4 , separately), about twice folds than the pristine PA membrane (8.1 L m −2  h −1 bar −1 ). This work displays an innovative method for the establishment of high-performance TFC NF membrane and deciphers new insights into the mechanisms of how the 2D nanoflakes interlayer dominate IP procedure and affect the ions sieving performance.