Construction of inter phase covalent bonding in ZIF-7-NH2(x) particles doped PA TFN membranes for improved reverse osmosis performance

To improve interface compatibility between ZIF-7 particles (PTs) and polyamide (PA) and reverse osmosis (RO) performance of thin film nano-composite (TFN) membranes, ZIF-7-NH 2 (x) particles (PTs) with different levels of -NH 2 substitution were synthesized by reacting Zn(NO 3 ) 2 with mixed ligand under different preparation conditions. The impact of their residual surface functional groups (SFGs) on the formation of inter-phase covalent bonds (ICBs) in PA separating layers were investigated relating to the inter-phase compatibility and salt rejection performance of the formed composite RO membranes. Doping ZIF-7-NH 2 PTs with ICBs could avoid the expansion of PA in acidic condition. Surprisingly high chemical stability was observed for ZIF-7-NH 2 PTs wrapped in the PA separating layers in TN membranes in the pH range of 2–13. TN(50)-0.15 membranes with strong ICBs showed 3 times higher water flux of 76 L·m −2 ·h −1 under 5.5 MPa at a high salt rejection of 98.7 %.