One-Step Reductive Electrodeposition of MOF Film on Polymer Membrane

Abstract

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 interface 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.

Cathodic deposition of MOF films: mechanism and applications

“…Afterward, the same group proposed a modified cathodic deposition method that achieves the direct deposition of HKUST-1 film on polyethersulfone (PES) membranes. 86 The PES-supported HKUST-1 film also showed a dye removal performance which is similar to the HKUST-1@paper membrane. Those HKUST-1 films can also work in ethanol solutions.…”

Electrochemistry-Induced Direct Deposition of Nanoscale Thin Zeolitic Imidazolate Framework-8 Films on Insulator Substrates

“…28,29 Interestingly, there are two recent papers that report direct MOF deposition on the surface of a non-conductive porous polymer membrane via anodic and cathodic approaches. 30,31 In the former, 30 HKUST-1 was grown on a porous poly(ether sulfone) membrane as a result of the counter-diffusion of anodically produced Cu 2+ across the membrane. In the latter, 31 HKUST-1 was formed on a porous poly(ether sulfone) membrane based on the cathodic formation of a base (OH − ) from NO 3 − at the underlying electrode and its permeation through the porous membrane, followed by the deprotonation of a ligand to form the MOF on the membrane.…”

“…30,31 In the former, 30 HKUST-1 was grown on a porous poly(ether sulfone) membrane as a result of the counter-diffusion of anodically produced Cu 2+ across the membrane. In the latter, 31 HKUST-1 was formed on a porous poly(ether sulfone) membrane based on the cathodic formation of a base (OH − ) from NO 3 − at the underlying electrode and its permeation through the porous membrane, followed by the deprotonation of a ligand to form the MOF on the membrane. In both cases, the permeation of Cu 2+ or OH − across a porous membrane was considered as the key process for the electrochemically assisted MOF deposition on the porous insulator membrane.…”

“…However, the deposition of an insulator leads to the passivation of the electrode and thus yields a film of limited thickness. , Furthermore, electrochemical approaches have rarely been employed to form insulator films on non-conductive substrates. Indeed, non-conductive porous membranes are usually coated with metal layers prior to electrodeposition for fabricating MOF-based separation membranes. , Interestingly, there are two recent papers that report direct MOF deposition on the surface of a non-conductive porous polymer membrane via anodic and cathodic approaches. , In the former, HKUST-1 was grown on a porous poly(ether sulfone) membrane as a result of the counter-diffusion of anodically produced Cu 2+ across the membrane. In the latter, HKUST-1 was formed on a porous poly(ether sulfone) membrane based on the cathodic formation of a base (OH – ) from NO 3 – at the underlying electrode and its permeation through the porous membrane, followed by the deprotonation of a ligand to form the MOF on the membrane.…”

“…Indeed, non-conductive porous membranes are usually coated with metal layers prior to electrodeposition for fabricating MOF-based separation membranes. , Interestingly, there are two recent papers that report direct MOF deposition on the surface of a non-conductive porous polymer membrane via anodic and cathodic approaches. , In the former, HKUST-1 was grown on a porous poly­(ether sulfone) membrane as a result of the counter-diffusion of anodically produced Cu 2+ across the membrane. In the latter, HKUST-1 was formed on a porous poly­(ether sulfone) membrane based on the cathodic formation of a base (OH – ) from NO 3 – at the underlying electrode and its permeation through the porous membrane, followed by the deprotonation of a ligand to form the MOF on the membrane. In both cases, the permeation of Cu 2+ or OH – across a porous membrane was considered as the key process for the electrochemically assisted MOF deposition on the porous insulator membrane.…”