Design And Synthesis Of A Novel Three-dimensional COF And Study On Its Fluorescence Properties

Covalent Organic Framework(COF)is a new class of crystalline organic porous materials composed of C,H,O,N atoms.It is characterized by its large volume,low density,high crystalline content,and controlled bulk.It is widely used in gas storage,photocatalysis,heterogeneous catalysis,sensing and optoelectronics,etc.It has become one of the key research directions of materials discipline in recent years.Since COFs materials were first reported,researchers have conducted in-depth studies on COFs,but most studies focus on two-dimensional COFs materials.There are few reports on threedimensional COFs,and there are only less than 20 kinds of three-dimensional topological structures.It is difficult to obtain high crystallinity 3D-COFs because of the harsh reaction conditions of 3D-COFs.Compared with 2D-COFs,3D-COFs are characterized by greater specific surface area and more stable properties,and have a wider application prospect in many fields.Therefore,a new type of 3D-COFs ligand was designed and synthesized in this paper,and a new type of 3D-COFs material was further synthesized from it.1.In this paper,we designed and synthesized a back-to-back double-bowlshaped three-dimensional ligand A5-CHO,which is an unreported construction unit of 3D-COFs and can be used for the synthesis of 3D-COFs.In addition,the Schiff base condensation reaction between ligand A5-CHO and benzidine was further performed by solvothermal method to obtain novel 3D-COFs(3D-COF-2).By means of NMR,MALDI-TOF,FT-IR,XRD and other characterization methods,we proved the successful synthesis of ligand A5-CHO and 3D-COF-2,and 3D-COF-2 has high thermal stability.The successful synthesis of a novel dodeconic three-dimensional ligand has contributed to the study of 3D-COFs structure and provided a new idea for the study of 3D-COFs structure in the future.2.The fluorescence property of 3D-COF-2 was also tested in this paper,and the results showed that 3D-COF-2 has excellent fluorescence sensing property,and can realize the high selectivity and sensitivity detection of Al3+by inhibiting the photoelectron transfer(PET)mechanism,which is free from interference in the presence of a variety of metal salt ions.In addition,3D-COF-2 can also detect TNP with high selectivity and sensitivity.The successful synthesis of 3D-COF-2 and its excellent fluorescence properties promote the development of 3D-COFs materials in the field of fluorescence sensing,and promote the further exploration of the structure of 3D-COFs.