Mixed-matrix gel for direct atmospheric water harvesting
Opportunity
Fresh water is abundant in the atmosphere, but this ubiquitous resource has yet to be harvested efficiently. Current atmospheric water sorbents require a desorption step that relies on steady solar irradiation. However, the overall water collection rate is still limited by the sluggish kinetics of sorption-desorption, the availability of sunlight only during the day and the need for iterative sorption-desorption steps, which limits on-demand desorption and hence the efficiency of water harvesting.
This invention addresses these limitations by introducing a mixed-matrix gel material (PC-MOF) to capture and deliver atmospheric water. This approach enables simultaneous and uninterrupted sorption-release of atmospheric water at minimal energy cost. PC-MOF with adaptable nature can accelerate the sorption/desorption kinetics and augment the water uptake, offering an efficient solution for atmospheric water harvesting process.
Market size/applications
According to the United Nations (UN-Water), 2.3 billion people live in water-stressed countries, and 733 million of them live in extremely and critically water-stressed countries. By 2030, it is estimated that around 700 million people could be displaced due to widespread water scarcity. One potential solution is atmospheric water harvesting, which is estimated to be a vast source of freshwater at 12900 km3. This invention with high liquid delivery efficiency and low energy cost can not only tackle water scarcity but also unlock economic potential, especially in water-scarce regions with agricultural constraints.
Technology
This invention involves the introduction of mixed-matrix gel (PC-MOF) for atmospheric water harvesting and delivery. The design of PC-MOF uses a non-swelling crosslinked polymer to integrate with a water-stable MOF, which enables the restricted volumetric transition and improves the moisture harvesting affinity. These designs improve water coalescence and transport within the MOF-polymer pores, resulting in autonomous water collection. In test, the gel exhibits a remarkable uptake capability and direct water release property, producing 6 grams of fresh water per gram of sorbent at 90% relative humidity (RH) per day without active condensation.
Firstly, our MOF material has remarkable water-stability, high equilibrium water uptake and fast sorption kinetics, which achieves to a total liquid delivery efficiency of 95% and an autonomous liquid delivery efficiency of 71%, the record among reported atmospheric water harvester. Secondly, the use of non-swelling crosslinked polymer enables restricted volumetric transition and steric pressure, and ionic grafting is used in its activation to improve the moisture harvesting affinity. These unique properties enable continuous water delivery for 1440 hours, with water production of 24-28L/day at relative humidity of 70%-90% respectively, indicating its potential in long-term operational stability. Thirdly, the standalone airborne water supplier gel offers a promising solution for achieving robust, sustainable and decentralized water production in different climatic conditions at minimal energy cost.
Fig. 1 Design of the autonomous airborne water supplier
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