Preparation And Adsorption Properties Of Rigid Or Flexible Metal-Organic Skeleton

Metal-organic frames are porous materials assembled from metal ions and organic ligands.Due to its advantages of large specific surface area and hydrophobic benzene structure,it can be applied to adsorb pollutants in water.Micropollutants ibuprofen,niacin and niacinamide were detected in a wide range of water pollutants that needed to be reduced.The method of adsorbent adsorption separation is widely used in the removal of drugs in water due to the simple operating conditions and the possibility of recovering the absorbed substances.Therefore,three rigid or flexible MOFs adsorption materials were prepared by hydrothermal method to adsorb the micropollutants ibuprofen,niacin and niacinamide in water to achieve effective removal of organic pollutants in water.Using chromium nitrate nonahydrate as the chromium source,the rigid metal-organic framework MIL-101（Cr）、Ui O-66;the flexible metal-organic framework MIL-53（Cr）was successfully prepared by solvothermal method and a series of characterizations such as XRD,FT-IR,TG,BET,SEM,etc.was also performed.The main work is as follows:（1）The adsorption capacity of MIL-101（Cr）on ibuprofen,niacin and niacinamide at 298 K was 110.590 mg·g^-1,54.769 mg·g^-1 and 3.322 mg·g^-1,respectively.The adsorption of MIL-101（Cr）on ibuprofen and nicotinic acid followed pseudo-first-order kinetics,and the adsorption of nicotinamide followed pseudo-second-order kinetics.All three follow the langmuir adsorption model.The increase of temperature is not conducive to drug adsorption,indicating the exothermic properties of adsorption.After five repeated cycles,the removal rates of MIL-101（Cr）for ibuprofen,niacin and niacinamide could still reach 88.46%,31.24%and 8.55%,showing good cycling performance.（2）At 298 K,the adsorption capacity of ibuprofen,niacin and niacinamide was 90.287mg·g^-1,53.428 mg·g^-1,3.084 mg·g^-1,respectively.The adsorption of Ui O-66 on the three models followed the pseudo-second-order kinetics and langmuir adsorption model.The increase of temperature is beneficial to drug adsorption,indicating the endothermic property of adsorption.After five repeated cycles,the removal rates of ibuprofen,niacin and niacinamide could still reach 91.22%,87.83%and 10.30%,respectively,which showed that Ui O-66 was reproducible and had good adsorption performance.（3）The adsorption of MIL-53（Cr）on ibuprofen,niacin and niacinamide showed that the maximum adsorption capacity of MIL-53（Cr）on ibuprofen,niacin and niacinamide at 298 K was91.533 mg·g^-1,5.997 mg·g^-1,6.868 mg·g^-1,respectively.The adsorption of MIL-53（Cr）followed pseudo-second-order kinetics,and the adsorption of ibuprofen and niacin was consistent with langmuir adsorption model.The adsorption of niacinamide conforms to Freundlich adsorption model.The increase of temperature is beneficial to drug adsorption,indicating the endothermic property of adsorption.After five repeated cycles,the removal rates of MIL-53（Cr）to ibuprofen,niacin and niacinamide could still reach 82.13%,5.45%and 35.84%,showing good drug removal ability.The dynamic simulation of adsorption molecules between MOFs and ibuprofen,niacin and niacinamide showed that there was strong aromatic ring stacking and hydrogen bond interaction between the three adsorbents and ibuprofen,and they all had the best adsorption effect on ibuprofen,which was consistent with the experimental results.