Metal organic frameworks as water harvester from air: Hydrolytic stability and adsorption isotherms

The crisis of potable water is an important issue among the world's population. This is alluring the attention of researchers and become the pivot area of research into environmental chemistry. Researchers are looking to address this issue in water harvesting from the air in an inexpensive manner. Therefore, the purpose of this review is to find efficient materials for water harvesting which is an absorption-based passive process with adsorbing water vapour in the atmosphere that can be modified for high working capacity, pressure and temperature responses. Metal organic frameworks (MOFs) are promising tools to act as adsorbents for harvesting water from air to address the problem of drinking water in arid areas around the world. The present review describes the hydrolytic stability of MOFs and the chemical and structural factors that affect it. The degradation mechanism of adsorption and general characterization methods used for the study of MOFs are outlined. Here, kinetic and thermodynamic parameters affecting hydrolytic stability are also discussed. The adsorption /desorption mechanism in various MOFs have been discussed to address the role of functionalities and hydrophilicity. In addition to this water adsorption isotherms which give the idea about the performance of adsorbent with respect to adsorption/desorption cycle. Structural and compositional parameters such as organic ligands, metal nodes and defects which are required for altering adsorption/desorption behaviours of MOFs and to improve working capacity of adsorbent have also been taken into consideration. In future for efficient water capture, electrified devices incorporated with MOFs could be used to operate many cycles per day.