The Synthesis Of Heterocyclic Supramolecular Compounds Containing Imidazole And Its Adsorption Of SO₂

With the rapid development of modern industry,many kinds of toxic gases were emitted into the atmosphere,which has led to a series of environmental problems.Sulfur dioxide is one kind of the toxic gases that cause more harm to the environment,it combines with the water in the air to form acid rain,which may cause harm to animals and plants and buildings.Therefore,reducing sulfur dioxide emissions and improving its treatment efficiency is one of the effective ways to solve current environmental problems.At present,the industrial treatment of sulfur dioxide is relatively simple,commonly using alkaline aqueous solution or wet sulfuric acid technology.However,these methods can not completely remove sulfur dioxide,and they also produce a large amount of wastewater,corroded pipelines,and the cost of recycling is huge.In view of the problems existing in traditional treatment methods,the researchers have explored some new treatment methods,for example,the adsorption of sulfur dioxide with new materials such as zeolite and metal-organic frame structure（MOF）,but the cost of these materials is high and they are difficult to apply in industrial area.Porous organic materials offer advantages over metal-organic frames that require metal source assembly.Imidazole ring has a unique structure,connected with functional groups with specific functions,so that it is conducive to stability in the acidic environment formed by sulfur dioxide,the dynamic reversible imine bond in the Schiff base is the guarantee of the formation of a flexible structure with a certain cavity,and the premise of achieving the adsorption of gas molecules.In this paper,a series of imidazole heterocyclic schiff bases supramolecular compounds were designed and synthesized,and the ability of four supramolecular compounds to adsorb sulfur dioxide,the solubility of three supramolecular compounds,and the influence of different amine groups on the formation of imidazole heterocyclic schiff bases were studied.First,the study used aldehyde and amine condensation to synthesize supramolecular compound 5 and supramolecular compound M1.In order to enhance the nucleophilicity of the nitrogen-atom at schiff’s base,the electron group（methyl）was introduced on the basis of supramolecular compound 5 and supramolecular compound M1,respectively,to give supramolecular compound 6 and supramolecular compound M2.The structure of multidimensional nuclear magnetism（¹H-NMR,¹H-¹H COSY-NMR,¹H-¹H NOESY-NMR）and high-resolution mass spectrometry（ESI-MS）was used to determine its structure,and nitrogen adsorption-desorption experiments were performed on supramolecular compounds 5and supramolecular compounds1 to characterize their pore structures.Second,the adsorption and desorption of sulfur dioxide was performed on the four supramolecular compounds synthesized,and the adsorption performance of sulfur dioxide was explored by high resolution mass spectrometry（ESI-MS）and infrared spectrometer.It was finally found that supramolecular compounds 5,supramolecular compounds 6,and supramolecular compound Symulticules M2 all had chemical adsorption and physical adsorption of sulfur dioxide,of which physical adsorption played a leading role,while supramolecular compound M1 only had physical adsorption of sulfur dioxide.Through mass spectrometry,it was found that these four supramolecular compounds can still maintain their original structure after desorption,the loss of adsorption capacity is small and the adsorption capacity loss of supramolecular compound 6 is greater than the loss of adsorption capacity of supramolecular compound 5,and the loss of adsorption capacity of supramolecular compound M2 is greater than that of supramolecular compound M1,indicating that the regeneration capacity of supramolecular compound 5 and supramolecular compound M1 is stronger and more suitable for reuse.In order to explore the adsorption capacity of SO₂in depth,the isotherms of somaculate compound 5 and supramolecular compound M1 were studied,and the maximum adsorption of supramolecular compound 5 and supramolecular compound M1on SO₂at 298 k and 1 bar was 0.65 cm³/g and 0.63 cm³/g,respectively.Finally,the regenerative performance of supramolecular compound 5 was evaluated,and the regeneration efficiency was 78.5%after 5 cycles.Third,four aldehyde and amine condensation routes were designed,and different substituent groups were introduced into the imidazole nitrogen-atom to explore the solubility of the final compound and whether different substituents had an effect on the aldehyde bond angle.Experiments have shown that the length of the carbon chain on the imidazole nitrogen-atom can change the solubility of the compound,but the carbon chain on the imidazole nitrogen-atom has no effect on the bond angle of the aldehyde group.Finally,the different amine groups and the compound 3 synthesized in the second chapter are subjected to the aldehyde and amine condensation reaction,to explore whether different amine groups have an effect on the formation of imidazole heterocyclic schiff bases,and finally found that the amine groups have an impact on the formation of imidazole heterocyclic schiff bases,different amine groups will make imidazole heterocyclic schiff bases more inclined to a certain ring structure when formed,in this experiment it would be more inclined to form the[2+2]structure.