Electric Rectification by a Redox-Conductive Metal-Organic Framework Bilayer Electrode

Unidirectional electron flow is essential for applications in electron storage and reconfigurable electronics, and traditionally realized in semiconductor junctions and even single-molecule concepts. Combining aspects from both technologies, redox-conductive metal-organic frameworks (RC-MOFs) exhibit molecule-like behavior in a crystalline, porous matrix. Herein, we show that bilayer RC-MOF electrodes composed of sequentially deposited Zn(PMDI) and Zn(NDI) on fluorine-doped tin oxide (FTO) function as chemical free-energy-based rectifying junctions. Unidirectional electron flow arises from thermodynamically allowed, and spatially organized redox reactions at the Zn(PMDI)|Zn(NDI) interface. Showcasing the rectifying function, electrons that reach the outer Zn(NDI) layer in the FTO|Zn(PMDI)|Zn(NDI) configuration are trapped as NDI•− and cannot be recovered by applying an oxidative bias. Introduction of [Co(bpy)3]3+ to the electrolyte creates a source–drain situation that reveals the potential-dependent directional electron flow across the bilayer. These results position RC-MOF bilayers as programmable electrochemical diodes, with rectification governed by layer sequence and redox accessibility.