Construction And Application Of Fluorescence And Electrochemical Sensing Based On Porphyrin Metal Organic Frameworks

Metal organic framework（MOFs）,as a kind of porous coordination polymers（PCPs）,is formed by the self-assembly of metal ions or clusters with organic ligands.MOFs have attracted wide attention from researchers in many fields such as bioimaging and phototherapy,gas storage and separation,sensing,catalysis,etc.By designing reasonable pores or/and metal nodes,MOFs can be given excellent performance.In recent years,there have been many reports on the development of MOF materials as sensors for metal ions,pesticides,antibiotics,harmful gases,biological small molecules and other substances.Therefore,MOF is considered as one of the most potential sensing materials.However,most of MOFs are difficult to maintain stability in water and poor conductivity,which makes it difficult for MOFs to be widely used.The shortcomings of poor stability and conductivity of MOFs have great limitation for using them to build sensors.Researchers have developed strategies to solve these problems:such as direct design and synthesis of stable structure,post synthesis modification,composite with other functional materials to prepare better materials.In contrast,direct design and synthesis of stable structure is the most economical and practical method.For example,group IV metals（Ti,Zr,Hf,etc.）can form stable chemical bonds with carboxylic acid ligands,so some researchers are committed to developing highly stable group IV metals based MOFs.So far,a number of Zr-based MOFs materials have been reported,which can be stable in water or even in strong acid/alkali media,such as Ui O-66,MOF-525,NU-902,MIL-140,etc.These materials have been applied in electrochemical sensing,fluorescence detection and many other fields.At present,food safety and disease monitoring is one of the issues that people pay special attention to,and the target analytes that need to be analyzed and detected are more and more diverse.Therefore,it is of great significance to build a simple and fast sensor and expand its application range according to different analysis objects.In this work,we used porphyrin compounds as organic ligands,which has excellent photoelectric properties,and prepared fluorescence probes and electrochemical sensors based on porphyrin MOFs by controlling metal ions for phosphate and glucose sensing,respectively.The main contents of this paper are as follows:1.We successfully synthesized the football-shaped porphyrin MOFs PCN-222 RPs,which based on water-stabilized Zr₆ clusters,and used for phosphate sensing through the fluorescence properties of the porphyrin ring.Its working principle is based on the special affinity of phosphate for Zr-O clusters,which allows phosphate to combine with it to form a Zr-O-P bond,dissociate the porphyrin ligand and emit obvious red fluorescence to realize the quantification of phosphate in aqueous solution.The method has high selectivity and good linear relationship in the range of 0-50μM,and the limit of detection（LOD）is 51 n M.At the same time,this detection method based on fluorescence enhancement strategy has also been successfully applied to detect Pi in two food samples,and its recovery rate of addition is 100.13%and 104.02%,showing high accuracy and reliability.2.In the presence of benzoic acid regulator,we have synthesized a micro graphene like material based on porphyrin metal organic framework,and successfully applied it to the non enzymatic sensing of glucose in alkaline medium.Based on the catalytic ability of Ni²⁺,glucose can be catalytically oxidized to gluconolactone under alkaline conditions,and the redox current can be generated to realize glucose detection.We used cyclic voltammetry to characterize the prepared Ni-TCPP/GCE and the catalytic performance for glucose in alkaline systems.And the amperometric method was used to record the current change after glucose was continuously added to 1 M Na OH during stirring to evaluate the concentration range of Ni-TCPP/GCE for glucose detection.The response current has a good linear relationship between the concentration of 0～4.1 m M,LOD is 6.46μM.The interference experiment results show that the interference signal of three coexisting biological small molecules（ascorbic acid,dopamine and uric acid）is strong in the detection of glucose by Ni TCPP/GCE,which has great limitations in practical application.Totally,we used porphyrin compounds and two kinds of metal ions to construct two kinds of sensors according to the properties of the materials to be detected,and apply them to the detection of target analytes inorganic phosphate and glucose.And both of them showing a good linear relationship and a wide detection range.This work provides ideas and methods for the design and construction of metal-organic framework-based sensors for the detection of target analytes in actual samples.