Study On Atmospheric Water Harvesting Driven By Solar Applying MOF Adsorbent With Improved Photothermal Property

With the increasing population and the continuous development of human economy and society,many countries and regions in the world are now facing the serious problem of fresh water scarcity.In the context of global freshwater crisis,there is an urgent need for a viable new technology to solve this problem.Atmospheric water harvesting driven by solar technology is a sustainable production of fresh water resources in an environmentally friendly manner using the air and vast reserves of solar energy found everywhere on earth.Among them,the sorption-based atmospheric water harvesting method is free from the constraints of the electric power system and is applicable to various extreme climates,and is also the solar air extraction method with the widest application scenario and the greatest potential.In the sorption-based atmospheric water harvesting driven by solar,the adsorbent performance fundamentally determines and limits the efficiency of the system water harvesting.In the existing studies,the adsorbent MOF-801(Metal Organic Framework)has been widely studied and applied due to its extremely high adsorption capacity and its applicability to a wide range of humidity.However,the strong interaction between the adsorbent and water molecules is conducive to rapid moisture absorption,but at the same time,the adsorbent needs higher heat to achieve regeneration,which restricts the practical application of the adsorbent.To solve the above problems,a high-efficiency atmospheric water harvesting cycle directly driven by solar energy has been constructed for the intermittent system.Analyzed the state change of wet air by combining the roles of each major part of the system.The principle of the system water extraction,the main parameters of the process of the water harvesting and the evaluation index of system performance are also described.It provides theoretical guidance for the development of composite adsorbent and the design of air water extraction device in the following.Based on the principle that carbon materials can enhance the photothermal performance of adsorbents,a composite adsorbent architecture was used to prepare three kinds of composite adsorbent with MOF-801 and three different carbon materials in this paper,characterizes the structure and morphology of each adsorbent,and proves that they all have the potential to be used as adsorbent for air-water extraction devices.On this basis,the effect of different carbon materials on the adsorption and desorption performance of MOF-801 adsorbent was comparatively studied.After analysis and preference,MOF-801/CNT adsorbent has the most significant improvement in photothermal properties.It was concluded that the adsorption capacity of MOF-801/CNT was improved by 10% and 30%,and the desorption rate was improved by 16.7% and 33.3% compared with MOF-801/CB and MOF-801/G.The effects of temperature,humidity and solar light intensity on the performance of the composite adsorbent were also analyzed,which proved that MOF-801/CNT has a good cycling stability and can be used as a composite adsorbent for air-water extraction devices.The MOF-801/CNT composite adsorbent was applied to build a small-scale atmospheric water harvesting device to demonstrate that the adsorbent is feasible for application in a real atmospheric water harvesting device,and the role of each component in the device is illustrated based on the controlled experiments.Finally,the performance of the air-water extraction unit was evaluated and it was shown that the average daily water production of the device was 1.51 kg/kg and has a high moisture recovery rate.