Facet Engineering of Metal-Organic Frameworks for Triboelectric Nanogenerators-Based Self-Powered Water Splitting

Metal-organic frameworks (MOFs) are highly versatile materials with tunable chemical and structural properties, making them promising for triboelectric nanogenerators (TENGs) and electrocatalysis. However, achieving precise control over MOF coordination structures to optimize facet-dependent properties remains challenging. Here, a facile and scalable dual-solvent synthesis strategy is presented to fabricate dendrite Co-2-methylimidazole MOF (ZIF-67-D), enabling tailored preferred facet and coordination environments. Using density functional theory (DFT) calculations and synchrotron-based X-ray absorption spectroscopy, it is demonstrated that ZIF-67-D, enriched with (112) facets, features a reduced Co coordination number and enhanced electron-donating ability compared to the conventionally (011) facet-dominated rhombic dodecahedron ZIF-67 (ZIF-67-R). This facet engineering boosts TENG charge density by 2.4-fold, OER current density by 9.9-fold (@1.65 V), and HER current density by 1.9-fold (@-0.3 V). The (112)/(011) facet ratio can be also tuned to precisely alter TENG output. Moreover, the optimized ZIF-67-D shows excellent stability, maintaining electrolyzer performance for 72 h and enabling TENG devices even in high humidity. Consequently, ZIF-67-D-based TENG (D-TENG) devices exhibit robust energy generation and power ZIF-67-D||ZIF-67-D electrolyzers for continuous hydrogen (H₂) production. These findings introduce a new paradigm for converting mechanical energy into sustainable chemical energy, offering insights into facet engineering for high-performance energy harvesting systems.