Preparation Of Covalent/Metal Organic Framework Materials And Research On Fluorescence Sensing Performance Towards Fe³⁺

Organic framework materials include metal organic framework materials（MOFs）and covalent organic framework materials（COFs）.MOFs composed of organic linkers and metal ions or clusters have become an emerging type of crystal materials with large specific surface area.Attributable to their high porosity and adjustable structure,MOFs have been widely studied and applied into various fields including gas storage and separation,heterogeneous catalysis,chemical sensing,etc.Covalent organic framework materials as a kind of crystalline porous organic polymers connected by organic structural units through covalent bonds possess the characteristics of highly ordered structure and regular pores,exhibiting great application potential in the fields of energy storage,adsorption and separation,catalysis and so on.In this paper,we have prepared two fluorescent sensors based on the above two materials.The main contents are listed below:In the first part,a nanocomposite material（coumaric acid@MOF）is constructed by metal organic framework materials（UIO-66）loaded with coumaric acid（7-hydroxycoumarin-4-acetic acid）,which can be employed as a ratio fluorescence senor to selectively detect Fe³⁺in the solution.The experimental results demonstrate that coumaric acid is successfully encapsulated in MOFs channels.And the structure of prepared coumaric acid@MOF presents a regular octahedron approaching a spherical shape.The resultant material with encapsulation structure shows the characteristic fluorescence emission of MOFs at 391 nm and the characteristic fluorescence emission of coumaric acid at 464 nm.The difference in the height and position of the two emission peaks makes the coumaric acid@MOF composite material as a self-calibrating luminescence sensor for detecting metal ions,which possesses the characteristics of strong anti-interference ability and high sensitivity.Moreover,the synthesized coumaric acid@MOF composite fluorescent probe exhibits outstanding selectivity and sensitivity as well as low detection limit.This work also provides a broader idea for designing MOFs and other coumarin derivatives to prepare ratio fluorescence sensors.In the second part,a covalent organic framework（COFs）material with fluorescence has been successfully synthesized by using 2,5-dihydroxyterephthalaldehyde and1,3,5-tris（4-aminophenyl）benzene raw materials and solvothermal method,which can also be employed as a fluorescent probe to detect Fe³⁺in the solution.When Fe³⁺exists in the solution,significant fluorescence quenching occurs without interference from other metal ions.The coordination of N and O chelating sites and the synergistic effect of the special pore structure give highly selective fluorescence quenching response.The fluorescence intensity of the fluorescence sensor at 425 nm exhibits a great linear relationship with the Fe³⁺concentration in the range of 2-20μM.This work provides an effective and simple method for detecting metal ions.