Water Harvesting from Desert Air Using MOF and Sunlight

Abstract

Metal-organic frameworks (MOFs) are an exciting class of crystalline porous materials composed of metal ions interconnected by organic linkers. In a recent paper in the Journal of American Chemical Society, it has been reported that researchers have synthesized MOF compounds with a surface area of more than 7000 m2 /gram. Available surface area of a spoonful of such MOF (about a gram of MOF), if utilised can cover an entire soccer field. There are numerous applications of this novel material like harvesting of water from any place and at any time, gas storage and separation, liquid separation and purification, catalysis, sensing, electrochemical energy storage etc. Even on the driest day in the desert, with an extremely low RH of 7% and temperature over 28°C, atmospheric water generator using MOF can produce 0.2 liters of water per kg of MOF/day making it ideal for people living in water starved areas. It can operate at ambient temperature using sunlight, and without any electricity. Further if MOF is mildly heated by electricity, a plant can be constructed which can work round the clock to produce sufficient water catering the needs of a village community or for a green house to grow vegetables in the desert. There are at present 90,000 types of MOFs. But some of them like MOF 303, 801, MIL 101 and a few other classes of MOFs are suitable for water harvesting purpose in arid areas. As there is plenty of sunlight in desert area, it is most convenient to genarate power by pv modules for water harvesting. But solar cells can not work at night and in cloudy days. But these limations can be overcome by using improved thermal storage system. Further integrating microprogrammed central unit (MCU) with the pv power system the power generation could be made controllable and adjustable.