| With the improvement of living standard,the influence of air humidity on physical health,material production and storage has been paid more and more attention.The annual energy consumption of China's humidity control system is up to 200 million tons of standard coal,which has become the focus of energy-saving and emission-cutting.Adsorption dehumidification is the most potential energy-saving humidity control method due to its advantages of high efficiency,continuous and reliable operation,flexibility and energy-saving.Particularly,the performance of the adsorption materials plays an important role in promoting the dehumidification effect.Therefore,it is of great scientific and practical value to develop energy-saving dehumidifying materials with high water adsorption capacity,high adsorption-desorption rate,easy regeneration,stability and low cost.Zr-based metal organic frameworks(Zr-MOFs)are one of the most popular moisture-absorbing materials because of their excellent water stability and water adsorption.Zr-MOFs have been synthesized by solvothermal method,which usually used a large amount of N,N-dimethylformamide(DMF).However,DMF is harmful to environment and human health,which restricts the industrial application of Zr-MOFs.Therefore,this paper focuses on the green synthesis method and structural performance optimization research of Zr-MOFs,and the specific contents are as follows:(1)In this paper,zirconium oxychloride and fumaric acid were used to synthesize Zr-MOFs in acetic acid/water by hydrothermal method,and a series of Zr-fuma-S porous metal organic frameworks were successfully synthesized.The structure of the synthetic Zr-fuma-S was analyzed by XRD,FT-IR and N2 adsorption isotherms.The results show that the resulting Zr-fuma-S material is similar to the MOF-801 structure.The BET surface area of Zr-fuma-S is 680 m2/g,which is lower than the classic MOF-801 material.The pore size distribution is broadened,and itis good for the desorption of water molecules.(2)Based on the study of the synthesis of Zr-fuma-S in acetic acid/water,the effects of process conditions such as reaction temperature,reaction time,acetic acid/water volume ratio,washing solvent and material composition were systematically investigated.The crystal and texture properties of the product obtained were characterized.The results show that the sample in acetic acid/water volume ratio of 1 reacted at 95? for 24 hours and washed with methanol has the largest BET surface area of 740m2/g and a high yield more than 90%.(3)In order to further reduce the synthesis cost of Zr-MOF-S materials,the effects of different zirconium sources such as zirconium hydroxide,basic zirconium carbonate and zirconium nitrate on the synthesis of Zr-MOF-S materials were investigated.The results show that the structure of Zr-MOF-S synthesized by zirconium hydroxide as the source of zirconium is consistent with that of the zirconium oxychloride source,but the yield is difficult to exceed 30%.Porous Zr-MOFs synthesized with basic zirconium carbonate and zirconium nitrate as a zirconium source all have lower crystallinity,high yields more than 90%,and lower specific surface areas about 300 m2/g.(4)The water adsorption properties of the synthesized Zr-MOFs were studied.The results of variable temperature water adsorption studies show that the water desorption of almost all samples are below 105?.And the desorption temperature of samples synthesized by zirconium hydroxide is below 60?,which has obvious advantages.The results of isothermal water adsorption studies show that the samples synthesized by zirconium hydroxide have the best water adsorption performance,with a maximum water absorption of 31%,and the yield needs to be further improved.The porous materials synthesized with basic zirconium carbonate and zirconium nitrate as the source of zirconium can also meet the demand.The maximum water absorption is up to 24%and 19%respectively,which greatly reduces the synthesis cost of zirconium metal organic frameworks. |
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