Direct Growth of Zn−Co MOF Thin Films for High-Performance Triboelectric Energy Harvesting and Self-Powered Devices

Abstract

Triboelectric nanogenerators (TENGs) are promising for harvesting low-frequency mechanical energy, yet their performance is often limited by the low charge density and modest dielectric properties of commonly used polymer triboelectric materials. Although metal−organic frameworks (MOFs)- based TENGs have been explored to enhance performance, most MOF-based TENGs use MOFs as filler materials, thereby restricting their intrinsic surface functionality and triboelectric nature. Herein, we report the direct growth of bimetallic Zn−Co MOF thin films on aluminum substrates using the hydrothermal method and use them as standalone triboelectric layers in a vertical contact−separation TENG configuration. Systematic variation of the Zn:Co molar ratio enabled modulation of surface morphology and triboelectric performance. Surface potential measurements confirmed the tribopositive nature of the Zn−Co MOF film and experimentally established its relative position in the triboelectric series. Among the investigated compositions, the Zn:Co (1:3) film exhibited optimal performance, delivering an open-circuit voltage of 490 V, a short-circuit current of 125 μA, and a peak power density of 10.42 W/m2 at 1 MΩ load resistance. The enhanced performance may be attributed to the combined effects of bimetallic composition and increased effective contact area. The best-performing TENG device powered a series-connected 480 light-emitting diodes and portable electronic devices using an energy storage element, demonstrating its practical applicability. The present work establishes a simple and scalable method for directly integrating bimetallic MOF thin films as an active triboelectric layer for high-performance triboelectric energy harvesting systems and self-powered device applications.