A general electrochemical strategy for oriented porphyrin-based MOF films with enhanced charge-transport kinetics

Abstract

The orientation is the key factor to determine the physicochemical properties of the metal-organic framework (MOF) films. New strategies for oriented MOF films are of fundamental importance in the advancement of science and technology. Here we report a unified approach to the synthesis of a large variety of porphyrin-based MOF films with different directions, chemistries and properties. This strategy is based on a general electrochemical regulation of coordination process of different metal cation (M1 = Zn, Co, Ni, Ce) and tetra (4-carboxyphenyl) porphyrin (M2TCPP, M2 = H, Cu, Pt, Pd) on various conductive substrates. The cathode strategy relies on the reduction of M2TCPP ligands and follows the electrochemical reaction mechanism to achieve effective control over crystallizing M1-M2TCPP MOF films oriented in the (110) direction. The highly oriented M1-M2TCPP MOF films are endowed with excellent crystalline, spatial network structure and hierarchical three-dimensional pore structure, which is conducive to charge transfer and material transmission and suitable for use as an electrochemical catalyst. The Zn-TCPP MOF films on conductive substrate could be used directly as an electrochemical sensor for electrocatalytic oxidation of NaNO2, and showed wide linear range, low limit of detection (0.24 μM), high sensitivity (285.8 mA/(mM·cm2)) and good anti-interference performance. We believe our methodology provides a simple and convenient route to a variety of oriented porphyrin-based MOF films for nanodevices with novel structure and function in nanotechnology.