Chirality-Driven Piezocatalysis in MOFs: Achieving Efficient Cocatalyst-Free Hydrogen Evolution

Metal-organic frameworks (MOFs) have emerged as promising catalysts for energy conversion, yet their application in piezocatalysis is severely hindered by intrinsically high symmetry, which leads to a weak piezoelectric response. Herein, we report a chirality-driven post-synthetic modification strategy to enhance the piezoelectricity of MOF-808(Hf) by grafting chiral L-histidine (L-His) onto Hf₆ clusters. Compared with MOF-808(Hf), MOF-808(Hf)-His exhibits a significantly enhanced piezoelectric response, with the d₃₃ coefficient increasing from 44.2 to 108.8 pm/V. This enhancement is attributed to the introduction of L-His, which breaks the structural symmetry and introduces the C═N bond as a highly stress-sensitive polarization center. Consequently, a stronger built-in electric field is generated under mechanical stress, promoting efficient charge separation and migration. Meanwhile, the grafted L-His lowers the hydrogen evolution barrier, with ΔG_H* decreasing from 0.46 to 0.37 eV, and further to 0.32 eV under stress. Consequently, without any cocatalyst, MOF-808(Hf)-His achieves an exceptional piezo-catalytic H₂ evolution rate of 5215.70 µmol g^-1 h^-1, 23-fold higher than that of MOF-808(Hf), and the highest among all reported MOF-based piezo-catalysts. This work establishes a robust chirality-driven approach to overcome the intrinsic limitations of MOFs in piezocatalysis, offering a versatile pathway for sustainable hydrogen production from mechanical energy.