Preparation Of Modified Copper-based MOF And Their Adsorption Of SO₂ And CO₂

Sulfur dioxide（SO₂）and carbon dioxide（CO₂）are two common gaseous pollutants,which have caused great harm to environment and people.The adsorption method has the preponderances of simple operation,excellent adsorption effect and recyclable regeneration,and has become a major research hotspot.Therefore,finding an adsorbent cost-effective and environmentally friendly to adsorb SO₂ and CO₂ is one of the great ways to alleviate gas pollution.The copper-based metal organic framework（CuBTC）has ultra-high specific surface area and the internal regular and orderly micropores that bring potential application in gas adsorption.The surface contains a large number of micropores and mesoporous,which provide a large number of adsorption sites for the adsorption of pollutants and lay a foundation for the further modification o f MOF.In order to further improve the adsorption performance of CuBTC and improve the instability of CuBTC,this paper uses CuBTC as the base material,which can adjust its structure to obtain the target physical and chemical properties,and uses Dicationic liquid（DILs）and Graphene oxide（GO）to modify CuBTC.CuBTC@GO and DIL/CuBTC were prepared for the adsorption of SO₂ and CO₂in the atmosphere.The relevant research conclusions are as follows:（1）CuBTC was synthesized by hydrothermal synthesis method and rapid synthesis at room temperature method,and modified by self-prepared GO.The new composites CuBTC@1.2%GO and CuBTC@2.4%GO were used XRD,SEM,FTIR,TG and BET characterize.The interaction between CuBTC@GO and SO₂were analyzed.CuBTC,CuBTC@1.2%GO and CuBTC@2.4%GO were successfully prepared.（2）In order to study the adsorption performance of CuBTC,CuBTC@1.2%GO and CuBTC@2.4%GO on SO₂,various factors（GO modification amount,preparation method of adsorbents,contact time,adsorbent reaction amount,SO₂concentration before adsorption and temperature,etc.）were investigated on the SO₂ adsorption.The results show that the optimal dosage of CuBTC and CuBTC@GO in the adsorption process is 200 mg.The lower of SO₂concentration before adsorption,the better the adsorption effect in a short time.However,it does not affect the removal rate under adsorption equilibrium.The static kinetic study found that rapid adsorption occurred in the first 0.5 min,then slowed down and reached equilibrium in about 20 min.When the GO loading is1.2%,showing the best adsorption performance.（3）The adsorption kinetic model fitting,isothermal adsorption model fitting,and adsorption thermodynamic analysis of the adsorption data of the CuBTC@GO/SO₂ adsorption system were carried out.The adsorption kinetic results showed that the SO₂ adsorption behaviors of CuBTC and CuBTC@GO were in accordance with the standard second-level dynamics model.The SO₂adsorption data of CuBTC@1.2%GO conforms to the Freundlich adsorption model.The q_m at 288 K is 72.49 mmol g^-1.In addition,the thermodynamic model shows that SO₂ adsorption is exothermic and spontaneous.The low temperature promoted the adsorption of CuBTC@1.2%GO on SO₂.（4）Two novel DILs,[C₄（im）₂]Br₂ and[C₄（Vim）₂]Br₂,were prepared by one-step synthesis.CuBTC prepared by the rapid synthesis method at room temperature modified with DILs by impregnation method.Two corresponding adsorbents,DIL-1/CuBTC and DIL-2/CuBTC,were prepared.XRD,SEM,FTIR,TG and BET were used to characterize the CuBTC before and after modification.The interaction between DIL-1/CuBTC and DIL-2/CuBTC and CO₂ was analyzed.CuBTC,DILs and DILs/CuBTC were successfully prepared.（5）In order to study the adsorption performance of DILs/CuBTC on CO₂,the influence of DIL modifying group,DILs/CuBTC amount,contact time,CO₂concentration before adsorption,etc.)was investigated.The results showed that the CuBTC modified with alkenyl-containing DIL significantly increased the adsorption rate and capacity of CO₂,and the dosage of DIL-2/CuBTC would reduce the average adsorption efficiency.When the adsorption time reaches 17min,the CO₂ concentration no longer affects the efficiency.（6）Adsorption kinetic model and isothermal adsorption model were fitting on the CO₂ adsorption system data of DIL-2/CuBTC.The adsorption kinetics results show that the CO₂ adsorption behavior of CuBTC and DIL-2/CuBTC conforms to the quasi-second-order kinetic model.At 293 K,the q_m of DIL-2/CuBTC to CO₂ is 49.41 mmol g^-1,which is 136.07%larger than CuBTC.（7）Regeneration experiments show that CuBTC@GO and DIL/CuBTC have an excellent adsorption effect and good recycling performance on SO₂ and CO₂after adsorption-desorption and cyclic adsorption for 5 times.（8）FTIR and BET characterization analysis of the materials before and after adsorption were carried out,and the adsorption mechanism in the two adsorption systems was discussed.The adsorption mechanism in the CuBTC@GO/SO₂system mainly involves the adsorption of Cu unsaturated sites and the pore filling effect,etc.the DIL-2/CuBTC adsorption system for CO₂mainly involves the electrostatic attraction（DIL/CuBTC protonated imidazole between N and H and CO₂）,Cu unsaturated site adsorption,π-πforce,and pore filling,etc.