Exceptional Long-Term Stability in Hydrogen Evolution via Defect-Engineered MIL-100 Synthesized by Controlled Thermolysis

Two quasi-iron-based metal-organic frameworks, Q-MIL-100 and Q-MIL-101, were prepared via thermal partial deligandation to create large-scale structural defects. This pore engineering enhanced the density of unsaturated iron sites and created hierarchical porosity, serving as active centers for the catalytic hydrogen generation from NaBH₄ hydrolysis. While pristine MIL-101 demonstrated higher activity than MIL-100, defect engineering reversed this trend, resulting in Q-MIL-100 achieving a superior hydrogen generation rate of 5360 mL·min^-1·g^-1 at 298 K, compared to 3360 mL·min^-1·g^-1 for Q-MIL-101. This enhanced performance is attributed to the synergistic combination of accessible active sites and an optimally restructured hierarchical pore architecture. Thermal activation to 313 K dramatically enhanced the hydrogen generation rates to 12,160 and 10,160 mL·min^-1·g^-1 for Q-MIL-100 and Q-MIL-101, respectively─a 2.3- to 3.0-fold increase over their performance at 298 K. The calculated activation energies were 41.7 kJ·mol^-1 for Q-MIL-100 and 56.2 kJ·mol^-1 for Q-MIL-101. A kinetic isotope effect indicated that the O-H bond cleavage in water was the rate-determining step. Q-MIL-100 demonstrated exceptional stability, retaining 92% of its initial activity after 16 reuse cycles. This work highlights the novel long-term stability of the engineered catalyst for practical hydrogen generation.