Cathodic Deposition of Conductive MOF Films: Mechanism and Applications

Abstract

Conductive metal-organic frameworks (MOFs) are porous yet electric conductive, promising for many applications such as electronics, electrocatalysts, and energy storage. However, traditional solvothermal and microwave synthesis methods usually lead to MOF powders that cannot be used directly, i.e., additional processes like adding binders, casting, and thermal treatments are required for their applications. Therefore, shaping conductive MOFs into 2D thin films is attracting attention from researchers. Here we report a cathodic deposition for the one-step fabrication of conductive MOF films, which features a fast and convenient deposition process. In this method, the deposition precursor contains metal salts and organic linkers (no supporting electrolyte is needed). When an external negative bias is applied on the conductive working electrode (WE), the linkers can be deprotonated on its surface. A conductive MOF film can thus be deposited on the WE by coordinating the deprotonated linkers and metal nodes. As demonstrating examples, Cu/Ni-HHTP (HHTP: 2,3,6,7,10,11-hexahydroxytriphenylene) and Cu-BTPA (BTPA: benzene-1,3,5-triyltriboronic acid) are cathodically deposited on indium-doped tin oxide (ITO) glass substrates. The measured conductivity of these deposited conductive MOF films varies from 0.01 to 0.1 S cm-1 depending on their thickness and composition. Both of the fabricated conductive MOF films show good performance on supercapacitors and electrochemical sensing.