Functionalized Metal-organic Frameworks For CO₂ Reduction Functionalization Into Nitrogen-containing Compounds

On the one hand,carbon dioxide（CO₂）is the main greenhouse gas that causes a series of environmental problems.On the other hand,CO₂ is also an abundant,low-cost,non-toxic and renewable C1 resource.Therefore,converting CO₂ into high value-added chemicals has been a research hotspot in recent years.Benzimidazoles,benzothiazoles and benzoxazoles have a wide range of pharmacological properties and biological activities and have a variety of therapeutic uses.Metal-organic frameworks（MOFs）are a new class of porous crystalline materials that are considered as ideal catalyst supports.In this paper,several functionalized metal-organic framework catalysts were developed for the green synthesis of benzothiazoles and benzoxazoles.The specific research contents are as follows:（1）3-（Pyridinium）-1-propanesulfonic acid（PS）was introduced into Py/MOF to synthesize immobilized organocatalysts[PS/Ui O-66（Zr）and PS/Ui O-67（Zr）]for the reductive cyclization of CO₂and o-phenylenediamine to obtain benzimidazole and to catalyze the N-formylation of monoamines.The morphology and structural characteristics of PS/MOF samples were characterized by various test methods such as N₂ adsorption and desorption test,CO₂-TPD,elemental analysis,TGA,XRD,XPS,SEM and TEM.3.2%-PS/Ui O-66（Zr）at 100℃and 3.0%-PS/Ui O-67（Zr）at 80℃respectively enable the quantitative synthesis of benzimidazole and are applicable to a wide range of benzimidazole derivatives Synthesis.In addition,PS/MOFs can promote the reductive N-formylation of CO₂ with monoamines.Theoretical studies show that the reaction energy barrier is significantly reduced from2.03 e V without catalyst to 0.97 e V in the presence of catalyst.After 8 recycling experiments,3.2%-PS/Ui O-66（Zr）still maintains good catalytic activity and structural integrity.（2）A heterogeneous catalyst 1.0%-Ir-Py/Ui O-67（Zr）was synthesized by immobilizing[Cp*Ir]units on Py/Ui O-67（Zr）via PSM of MOF.The morphology and structural characteristics of PS/MOF samples were characterized by various test methods such as N₂ adsorption and desorption test,ICP,XRD,XPS,SEM and TEM.The developed 1.0%-Ir-Py/Ui O-67（Zr）can quantitatively synthesize benzothiazole and benzoxazole at 100℃and 120℃,respectively.Through substrate expansion experiments,it is verified that the material is suitable for the synthesis of a series of benzothiazole and benzoxazole derivatives.1.0%-Ir-Py/Ui O-67（Zr）can still maintain good catalytic activity after six consecutive repeated recovery experiments.