Carbon quantum dot doped NH₂-MIL-53 for sustainable atmospheric water harvesting

Sorption-based atmospheric water harvesting (SAWH) using metal–organic frameworks (MOFs) presents a promising solution to freshwater scarcity in arid regions. However, despite the intrinsic presence of abundant binding sites and polar functional groups, the practical application of MOFs remains limited due to their low adsorption/desorption efficiency and challenges associated with industrial-scale deployment in bulk form. In this study, we developed a nanocomposite sorbent by doping carbon quantum dots (CQDs) onto the surface of NH₂-MIL-53(Al) via a hydrothermal method, ensuring the preservation of its original crystalline structure while enhancing its functionality. The hierarchical pore structure introduced by CQDs doping not only provides ample adsorption sites but also facilitates rapid moisture uptake and high solar-thermal conversion efficiency. As a result, the material exhibits a significantly improved adsorption/desorption cycle, achieving complete water uptake and release within 300 min (150 min for adsorption and 150 min for desorption under simulated solar irradiation). Moreover, the nanocomposite demonstrates a water uptake capacity of 0.01317 g·g⁻¹ at 20% relative humidity (RH) and 0.092 g·g⁻¹ at 80% RH, surpassing the performance of most state-of-the-art MOF-based SAWH materials. This work presents a simple yet effective strategy for enhancing the adsorption/desorption kinetics of NH₂-MIL-53(Al), offering valuable insights for the design of high-performance solar-driven water harvesting materials.