Enhanced atmospheric water harvesting (AWH) by Co-based MOF with abundant hydrophilic groups and open metal sites

Atmospheric water harvesting (AWH) is one of the effective measures to solve the problem of global freshwater resources shortage. Metal-organic frameworks (MOFs) with long-term stability and reversible high water uptake properties can be promising candidates for atmospheric water collection. However, the reported MOF adsorbents still have defects in saturation adsorption capacity. To further improve the water collection performance of MOF materials, a novel Co-MOF material with superior water vapor capacity has been developed in this work. The Co-MOF-31 synthesized via solvothermal method can achieve an adsorption capacity of 0.79 g/g at a low relative pressure of 0.30 and a saturated adsorption capacity of up to 0.98 g/g, which is attributed to rich open metal sites, substantial exposed hydrophilic groups and extremely high specific surface area (1619.3 m2/g) causing by the effective combination of the appropriate organic ligand and metal salt. Meanwhile, the Co-MOF-31 can maintain 96 % of the initial water adsorption amount after >20 water uptake and release cycles. This study will open the way for designing efficient MOF absorbents for AWH.