TiO₂-Engineered MOFs Activate Electron-Rich Ni Sites for Efficient and Durable Hydrogen Production

Controlling the electronic structure of non-noble metal active sites is the central challenge to unlocking fast and durable hydrogen release from hydrous hydrazine (N₂H₄·H₂O, 8.0 wt%), a promising liquid hydrogen-storage material. Herein, for the first time, we demonstrate that TiO₂-engineered NH₂-MIL-101(Cr) enables strong electronic metal-support interaction (EMSI) to generate confined electron-rich Ni active sites with an ultrafine size of 3.2 nm, thereby markedly accelerating the rate-determining N-H bond activation. As a result, the Ni/TiO₂-NH₂-MIL-101 delivers a turnover frequency (TOF) of 422 h^-1 at 343 K for N₂H₄·H₂O dehydrogenation, 28, 10, and 4 times higher than unsupported Ni NPs (15 h^-1), Ni/MIL-101 (42 h^-1), and Ni/NH₂-MIL-101 (98 h^-1), respectively, while maintaining 100% H₂ selectivity and exceptional stability over 20 cycles, outperforming the state-of-the-art nonprecious metal catalysts reported for this reaction. It also exhibits superior catalytic activity and robust durability toward hydrazine borane (N₂H₄BH₃, 15.4 wt%) dehydrogenation, achieving a TOF up to 881 h^-1 at 343 K. These findings demonstrate that TiO₂-driven electronic activation of Ni sites in MOFs offers a generalizable support-engineering strategy for efficient and durable hydrogen production from liquid hydrogen-storage materials.