Research on the Photothermal Conversion and Water Collection Performance of MOF-303 Composites for Solar-Driven Air Water Harvesting

Atmospheric water harvesting is a promising solution to freshwater shortage because it is not limited by location. Metal–organic frameworks (MOFs) have attracted much attention for low-humidity applications due to their large surface areas and strong water adsorption capacities. In this study, the desorption efficiency of MOF-based adsorbents under solar heating was improved by adding efficient photothermal materials. MOF-303 was combined with Fe 3 O 4, MWCNTs, and Ti 3 C 2 by ball milling. Characterization analysis of the composite materials’ morphology, elemental distribution, crystal structure, and functional group changes demonstrated that the composite formation was successful. The results showed that compared to the original MOF-303, adding 10 wt % photothermal material greatly improved light absorption, leading to faster solar heating and quicker water desorption. However, the introduction of photothermal materials leads to a reduction in the effective adsorption sites within the composite materials, resulting in lower saturated water absorption capacities for all three composites compared to the original MOF-303. Among the three composite materials, Ti 3 C 2 /MOF-303 shows the best overall performance. Under 40% RH conditions, the material increased water vapor adsorption from 0 g/g to 0.382 g/g within 30 min. After 20 min of irradiation at 1 sun, the surface temperature of the material rapidly rose to 87.4 °C, reducing the remaining water content to 11.3%. Under the same conditions, the original MOF-303 had a water vapor adsorption of 0.42 g/g, a surface temperature of 59.8 °C after irradiation, and a remaining water content of about 31.7%. Taking 30% RH as an example, the Ti 3 C 2 /MOF-303 water vapor adsorption capacity is about 8.1% lower than that of the original MOF-303. During desorption at 85 °C, it takes approximately 20 min to achieve complete desorption, which is 20% shorter than that of the original MOF-303.