44ª Reunião Anual Virtual da SBQ

Reversible water capture directly from atmospheric humidity can be used for both produce safe and clear water and humidity control1. Today, commercial sorbents, such as silica gel or zeolites are widely used despite having high-energy consumption and low recyclability due to their high affinity towards water molecules. Therefore, the development of new adsorption materials that can outperform traditional desiccants proves to be important2. Herein, we report the synthesis and characterization of a Co(II) coordination complex that can be used as a candidate for atmospheric water harvesting. The complex was synthesized adding a MeOH solution of Co(CH3COO)2.4H2O into a solution of an aminoacid ligand3 in 1:1 MeOH:H2O using a metal-ligand ratio 1:2. Single crystal X-ray diffraction revealed that the complex crystallizes in a monoclinic P21/n space group, with two ligand molecules coordinated in the equatorial plane and two water molecules completing the octahedral sphere. The crystalline structure is stabilized by hydrogen bonding between the complex units and uncoordinated water molecules in the asymmetric unit of the compound (Figure 1a). Water absorption/dessorption properties were studied by thermogravimetric analysis (TGA), shown in Figure 1b. The material was first heated at 155°C/ 30 min to complete water removal, which is accompanied by crystal color change. After crystal dehydration, three water capture tests were carried out: i) capturing water from air humidity, ii) from liquid water and iii) from water vapor at 60 °C. The results of these experiments were analyzed by TGA, which showed a maximum of 18 % of water uptake, e.g, an amount close to the initial water capacity of the complex. These absorption studies combined to the color change (Figure 1c) strongly indicate that the Co(II) complex hows a potential material for atmospheric water harvesting or dehumidification agent.