Potable water extraction from the atmosphere: Potential of MOFs

This communication addresses the Adsorptive Extraction of potable Water from the Atmosphere (AWEA) in arid areas using solar energy. The method includes a) adsorption of water vapor from the air at night-time, and b) desorption of the stored water and its subsequent collection in a condenser in the day-time. Metal-organic frameworks (MOFs), being crystalline porous solids with unique adsorption properties, might provide a promising avenue for AWEA. First, the thermodynamic requirements for adsorbent optimal for AWEA are formulated. The optimal adsorbent (OA) has energy different adsorption centers with the affinity distributed in a wide range of adsorption potential between ?F and ?F, corresponding to the adsorption and regeneration stages, respectively. For three arid climatic zones (the Sahara Desert, Saudi Arabia and Central Australia), the quantitative requirements to the OA are formulated in terms of the ?F and ?F values. The selection of MOFs, promising for the AWEA, is carried out. The most promising MOFs for Australia are MIL-101(Cr), CoCl(BTDD), and MIL-101(Cr)-SOH. MIL-160 and CAU-10(pydc) are appropriate for Saudi Arabia and Sahara. They exchange 0.34-1.6 (g water)/(g adsorbent) and allow getting the fractions ? = 0.78-0.93 of water extraction and ? = 0.75-0.90 of water collection at the regeneration temperature 75-100 °C.