Fig. 2. Isotherms of MOF-801 and design of the MOF-based water harvester for water production from desert air.

(A) Water sorption isotherms (adsorption, filled symbols; desorption, open symbols) of MOF-801 and MOF-801/G at 15°C (blue), 25°C (gray), and 85°C (red). In comparison to previously reported isotherms for MOF-801, a shift of the inflection point to higher relative pressures, a lower maximum capacity, and hysteresis were observed. These findings are related to a high degree of single crystallinity of the material (23). Blending MOF-801 with graphite led to a decrease of the gravimetric capacity corresponding to the added weight, while the general shape of the isotherm was fully retained. (B) Schematic of the water harvester consisting of a water sorption unit and a case. During the night, the cover of the case is opened, allowing the MOF to be saturated with moisture from desert air. During the day, the case is sealed to create a closed system. Humid hot air flows from the MOF to the condenser and is cooled down by heat rejection to the surroundings. When the dew point is reached, condensation occurs, and liquid water collects at the bottom of the case.