Electronic Doping of Metal-Organic Frameworks for High-Performance Flexible Micro-Supercapacitors

Abstract

The combination of high specific surface areas, well-defined porous structures, and redox-active sites renders the organic frameworks as promising electrode materials for next-generation energy storage devices. Despite the recent advancements in the fabrication of conductive metal-organic frameworks (MOFs), they generally require tedious synthesis procedures, which hinder their energy-related applications. Herein, a doping strategy using electron acceptor molecules is demonstrated to tune the ohmic electrical conductivity of MOF thin-film electrodes. For instance, the conductivity of MOF Cu3(BTC)2 film is enhanced over 40 times after doping with 7,7,8,8-tetracyanoquinododimethane (TCNQ). Thereby, asymmetric in-plane micro-supercapacitors (MSCs) are constructed utilizing in situ-grown TCNQ@Cu3(BTC)2 as the cathode and activated carbon as the anode, which delivers remarkable areal capacitance of 95.1 mF cm−2 at a scan rate of 5 mV s−1, superior to those of the reported MSCs (0.1–50 mF cm−2). Moreover, the fabricated devices show long-term stability with 94.1% capacitance retention up to 5000 charge-discharge cycles at 10 mA cm−2. The molecular doping engineering of organic framework materials with excellent electronic properties for energy storage and conversion applications is inspired.