A Comparative Study of MIL-100(Fe) Synthesized via Conventional and Green Methods for Water Harvesting

Water scarcity is one of the most urgent global challenges, with major environmental, social, and economic consequences. Atmospheric water harvesting (AWH) is emerging as a sustainable strategy to obtain water from air, especially in arid and semi-arid regions. Among the materials investigated for this purpose, Metal Organic Frameworks (MOFs) are particularly promising because of their high surface area, tunable porosity, and remarkable water adsorption properties, which allow efficient water capture even under low-humidity conditions. This study focuses on the synthesis and characterization of MIL-100(Fe), prepared through two different routes: a conventional solvothermal method and a greener synthesis carried out under milder conditions. The green procedure was designed to reduce the environmental impact of MOF production while preserving, or improving, the functional performance of the material. The sample obtained through this approach, named M100Fe-G, was compared with the conventionally synthesized material, M100Fe-T. The materials were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption measurements (BET) and dynamic vapor sorption (DVS). M100Fe-G showed higher crystallinity and superior water adsorption capacity than M100Fe-T. Although M100Fe-T exhibited a slightly higher specific surface area, M100Fe-G displayed an improved total pore volume, a key parameter for water harvesting applications. Water adsorption isotherms confirmed that M100Fe-G performs better across different humidity ranges, showing more efficient water uptake and release. Overall, these results demonstrate that sustainable synthetic strategies can reduce the ecological footprint of MOF production while enhancing material performance for AWH. Moreover, the proposed green synthesis was successfully upscaled to produce larger MOF quantities, enabling further engineering into pellets and coatings, which are currently under investigation to broaden the applicability of sustainable MOF-based materials for atmospheric water harvesting.