PPy-MOF-303@SA Aerogel Composite Adsorbent with Vertical Channels for Atmospheric Water Harvesting in Arid Environments: Preparation and Performance Evaluation

Abstract

Adsorption-based atmospheric water harvesting (AWH) is a promising approach to address freshwater scarcity, particularly in arid regions. The performance of AWH largely depends on the adsorbent. Traditional adsorbents often suffer from low moisture uptake and high regeneration temperatures, while emerging adsorbents such as polymer gels and metal-organic frameworks (MOFs) also face challenges like complex synthesis procedures. Although MOFs can adsorb water vapor under low-humidity conditions, their practical application is limited due to their powdered form.Here, we propose a composite aerogel adsorbent, PPy-MOF-303@SA, synthesized via directional freezing, which uses sodium alginate aerogel as the matrix, MOF-303 as the hygroscopic component, and polypyrrole as the photothermal component. By loading MOF onto the aerogel, the limitations of powdered materials are overcome. The vertically aligned channels formed in the aerogel enhance adsorption kinetics, while polypyrrole improves the photothermal conversion capability.The composite adsorbent achieves a water uptake of 0.39 g/g at 25°C and 30% relative humidity, reaching equilibrium within 60 minutes. Under 1 kW•m⁻² solar irradiation, the surface temperature reaches 72.7°C, with a desorption ratio of 96.73%.