Enhancing Atmospheric Water Harvesting of MIL-101 (Cr) MOF Sorbent with Rapid Desorption Enabled by Ni─Ni3S2 Photothermal Bridge

Abstract

Metal–organic frameworks (MOFs) have emerged as leading candidates for atmospheric water harvesting (AWH). Despite their high water uptake capacity, challenges persist in effective solar-driven desorption for water collection. Addressing this, a photothermal bridge is introduced by in situ growth of Ni₃S₂ coating on a thermally conductive nickel mesh, enhancing heat transfer to the MOF and accelerating desorption kinetics. MIL-101 (Cr) MOF in bulk form (BMOF) is bonded to the lightweight Ni─Ni₃S₂ mesh using adhesive, forming a dual-layer Ni─Ni₃S₂ mesh/BMOF assembly. This hybrid retains a high water uptake of ≈0.63 g g⁻¹ at 60% relative humidity (RH) with superior sorption kinetics. Photothermally driven heat transfer from Ni─Ni₃S₂ to BMOF achieves complete water desorption within 40 min under 1 kW m⁻². Compared to other configurations like foil, granules, and foam, the mesh-based hybrid has the highest single-cycle adsorption–desorption kinetic of 3.18 × 10⁻³ g g⁻¹ min⁻¹. Additionally, the hybrid demonstrates exceptional hydrothermal stability over 50 cycles and maintains morphological stability with airflow, ensuring consistent performance. Heat transfer simulations confirm the thermal distribution across the Ni─Ni₃S₂ mesh/BMOF, corroborating the rapid and uniform desorption. This approach paves the way for efficient AWH in high-RH, water-scarce regions by enhancing desorption kinetics through solar energy.