Study On MOFs/Porous Polymer Composites Based On Water Vapor Adsorption And Development Of Water Harvesting Device

Adsorption-based atmospheric water harvesting technology is expected to solve the problem of water scarcity and water stress in areas with underdeveloped water supply networks.The development of high-performance adsorbent materials and efficient water harvesting systems at low humidity is the key to water harvesting.In this paper,we designed a plate adsorption bed using a MOF material（ZJU-210）with high water vapor adsorption performance as an adsorbent,and combined with a heater and condenser to build an adsorption-based atmospheric water harvesting system for efficient water harvesting.However,the powder characteristics of ZJU-210 material seriously affected its performance in the water harvesting system.Therefore,MIL-160,also an aluminum-based MOF,was loaded into a surface-functionalized polyacrylate porous polymer（PAA-NH₂）carrier using an in situ growth method to prepare a spherical composite with high water vapor adsorption capacity at low humidity.The structure and microscopic morphology of the composite as well as the water vapor adsorption/desorption performance were investigated,and the main research of the paper is as follows:（1）An adsorption atmospheric water harvesting system was developed based on powdered ZJU-210 adsorbent material,where the adsorbent bed,heater and condenser were coupled to each other for efficient operation.The effects of adsorbent filling amount and different ambient humidity on the water vapor adsorption capacity of the adsorption bed were studied.The results showed that the water vapor adsorption capacity of the adsorption bed increased with the increase of filling amount,but the mass transfer rate showed a decreasing trend.the water vapor adsorption capacity of the adsorption bed increased gradually with the increase of ambient relative humidity,and reached a higher adsorption capacity at a relative humidity of20%;the effect of different adsorption/desorption times on the water collection capacity of the system was investigated,and the experimental results showed that when the adsorption bed was filled with 525 g of adsorbent material（15 adsorption plates）and with adsorption for 3.5 h and desorption for 2.5 h as one water collection cycle,the water collection can reach 59.57 g at an average relative humidity of 22.0%.After water quality testing,it can be seen that its conductivity,total hardness,acidity,turbidity and metal ion concentration(Cu²⁺,Fe²⁺,Zn²⁺and Al³⁺)are lower than the single standard required by the World Health Organization.（2）The porous polyacrylate polymer was prepared by emulsion suspension polymerization and grafting with tetraethylenepentamine to improve the hydrophilicity and internal surface energy of the carrier,and MIL-160 was loaded into the internal network of the porous carrier by in situ growth.The spherical composites with different MOF loadings were obtained by varying the impregnation concentration of metal salts and organic ligands,and the effects of different MOF loadings on the microscopic morphology,pore structure and water vapor adsorption properties of the composites were investigated.The results demonstrated that the specific surface area and pore volume of the composite increased with increasing of MOF loading,and the composite with 65wt.%loading had a specific surface area of 782.7 m²/g and a pore volume of 0.292 cm³/g,and exhibited high water vapor adsorption（0.252 g/g）at 15%relative humidity.In addition,the desorption can be completed at 80°C,and the activation energy of desorption was calculated as58.6 k J/mol.