Synthesis Of Covalent Organic Framework Materials Based On Benzothiadiazole And Their Applications In Catalysis And Fluorescence Sensing

Covalent organic framework（COF）is a group of porous organic polymeric materials obtained from covalently attached organic building blocks.They exhibit positional control in two-or three-dimensional spaces through the predesigned and specified bonding of the monomer linkers.COFs are considered as one of the most promising materials for applications in environmental remediation because of their ordered geometry,high porosity,functionality,high stability,and postsynthetic tunability in various physical and chemical forms.COFs have attracted a vast interest in recent time because of their potential in gas adsorption and separation,biomedicine,catalysis,photoelectric,energy storage and so on.Here,two novel COFs materials,TAPB-BTDA-COF and TAPP-BTDA-COF,were synthesized by the condensation reaction between the 1,3,5-tris（4-aminophenyl）-benzene（TAPB）and 5,10,15,20-tetrakis（4-aminophenyl）-21h,23h-porphine（H₂TAPP）.First,two novel Suzuki cross-coupling reaction catalysts based on COFs materials were prepared by post-modification method.The two COFs were postsynthetically modified by postsynthetic metalation,to obtain two modified metallic species,Cu-TAPB-BTDA-COF and Cu-TAPP-BTDA-COF.Among them,Cu-TAPB-BTDA-COF showed superior catalytic activity for Suzuki cross-coupling reaction.Then the effect of the catalyst loading,base,the solvents and reaction temperature were studied.Thus the optimal condition of this reaction were established as followed:5 mol%Cu-TAPB-BTDA-COF as the catalyst,K₂CO₃as base,ethanol（2.0 mL）as solvent,80℃,4 h.In addition,the COF gave good recyclability and could be reused after a simple separation manipulation.This investigation will provide a new insight about design and synthesis of novel modified metallic COFs with enhanced activities.Amines,as a class of persistent and highly toxic organic pollutants,have been posing a great threat to human health and the environment.Therefore,the design and preparation of a highly sensitive and selective luminescent probe to detect amines is important but challenging.Herein,by constructing the TAPP monomer with the ACQ effect into the covalent organic framework,fluorescent TAPB-BTDA-COF was constructed.Interestingly,TAPB-BTDA-COF exhibited excellent selectivity and sensitivity for aniline and trimethylamine sensing among various amine molecules.The K_svvalues of TAPB-BTDA-COF toward aniline and trimethylamine are 1.49×10⁵M^-1and 2.39×10⁴M^-1,respectively.TAPB-BTDA-COF exhibits unprecedented low detection limits of 27 and 170n M toward aniline and trimethylamine,respectively.In addition,TAPB-BTDA-COF displayed obvious fluorescence quenching response in methanol towards Fe²⁺and Pd²⁺with high selectivity.TAPB-BTDA-COF exhibits low detection limits of 1.4 and 0.2 uM toward Fe²⁺and Pd²⁺,respectively.This work indicated that the fluorescent COF as a fluorescence sensor has promising application in recognition and detection of specific organic amine and metal ions.