One-Step Reductive Electrodeposition of MOF Film on Polymer Membrane

Reductive electrodeposition is a technique for the preparation of substrate-supported MOF films but is generally incompatible with poorly or nonconductive substrates like polymers and suffers from the possible codeposition of metallic impurities. Here, we report a facile and inexpensive strategy that achieves one-step reductive electrodeposition of impurity-free MOF films (i.e., HKUST-1 film) on nonconducting poly(ether sulfone) (PES) membranes. Unlike previously reported reductive electrodeposition configurations, which only contain the electrode-electrolyte inter-face near the working electrode, there are two tandem interfaces in the proposed approach, namely, the electrode-membrane interface and the membrane-electrolyte interface. Owing to the counter-diffusion of ions across the polymer membrane, this strategy allows the generation of MOF units on the membrane- electrolyte interface, while the codeposition of metal happens on the other, resulting in the deposition of a pure MOF film on untreated polymer membranes. Importantly, thanks to the inherent "self-closing " ability of the proposed electrochemical approach, a compact polycrystalline HKUST-1 film supported on PES membrane was obtained under mild conditions, which exhibited a rejection of 98.7% for rose bengal in an aqueous solution with a permeance of 7.4 L m-2 h-1 bar-1.