Waste-derived aluminium based metal-organic framework for atmospheric moisture harvesting and photocatalytic hydrogen production

Green hydrogen production via photocatalytic water splitting is a promising and environmentally friendly route towards sustainable energy. However, there production of green hydrogen relies on freshwater source, which is limited in regions facing water scarcity. Herein, we report a waste-to-value approach in which aluminium nitrate nonahydrate metal source and benzene 1,4 dicarboxylic acid organic linker were derived from waste to synthesize MIL-53 (Al). The materials were characterised by various analytical techniques to confirm the successful synthesis. MIL-53(Al) exhibited a water-responsive porous structure with a water harvesting capacity of 180 g.kg⁻¹, while Al(NO₃)₃.9H₂O showed a superior capacity of 420 g.kg⁻¹. Kinetic studies revealed that water desorption followed pseudo second order kinetics, indicating site specific interactions. Reusability tests showed that MIL-53(Al) maintained nearly constant water production over five cycles (95% retention), whereas Al(NO₃)₃·9H₂O exhibited a gradual decline due to particle agglomeration. The water harvested from the atmosphere was used directly as the reaction medium for photocatalytic hydrogen production. MIL-53(Al) demonstrated a hydrogen production rate of 418 µmol. g⁻¹.min⁻¹ under visible light, with an apparent activation energy of 1.79 kJ mol⁻¹ and retained 96% of its activity after five cycles. The individual precursors show negligible photocatalytic activity. This work demonstrated a closed loop, waste-derived pathway that couples atmospheric water harvesting with solar driven hydrogen production, contributing to circular economy and sustainable energy.