Tuning of Electron-Donating Metal–Organic Frameworks toward High-Performance Triboelectric Nanogenerators for Self-Powered Shear Sensing

Triboelectric nanogenerators (TENGs), which convert mechanical energy into electrical signals, have emerged as apromising platform for self-powered motion sensing. However, the development of high-sensitivity TENG sensors remains limited by the availability of tunable and efficient tribo-positive materials, which are electron donors. In this work, we present a material design strategy based on the incorporation of electron-donating functionalized metal-organic framework (MOF) fillers into a polyurethane (PU) polymer matrix. Three functional groups (-CH₃, -NH₂, and -OH) were systematically studied to investigate their influence on triboelectric performance. The resulting composite membranes demonstrated tunable charge-donating behavior and improved electrical output, with the -OH-modified MOF yielding the highest electrical output of 197.6 ± 1.3 V and 0.47 ± 0.08 μA/cm², which are 2.3 and 3.2 times higher than that of the pristine PU. The enhanced charge-donating mechanism was elucidated through a combination of advanced micro- and nanoscale chemical and mechanical analysis. Theoretical calculations employing <i>ab initio</i> density functional theory (DFT) were performed to reveal the electron distribution within the periodic MOF structure. Furthermore, the practical application of the optimized TENG device was demonstrated in a single-electrode shear sensor configuration, exhibiting high sensitivity in sliding motion detection. This study highlights a scalable and biocompatible strategy for improving tribo-positive materials and advancing the performance of tunable TENG-based sensors to enable shear force monitoring.