Synthesis And Analysis Of Metal-organic Gels Based On Terpyridyl

Metal-organic gels?MOGs?,constructed by metal ions and organic small molecules through various noncovalent interactions such as ionic attraction,?-?stacking,hydrogen bonding and vander Waals interaction,are a new type of organic-inorganic hybrid materials.Due to their extraordinarily high surface area,good surface accessibility,permeability,stimuli-responsive properties and rapid mass transfer,MOGs have been widely applied to chiral recognition,proton conduction,catalysis,adsorption,and fluorescence sensor.Among the small organic molecules that form MOGs,the terpyridyl ligands tend to form ionic attraction,?-?stacking,hydrogen bonding and vander Waals interaction in the process of preparing MOGs.Based on this,this article focuses on a series of MOGs and their composite materials,which based on 4-[2,2'':6',2''-terpyridyl]-4'-phenylcarboxylic acid?Hcptpy?,such as Al-MOGs,Cu-MOGs,and AgNPs/MOGs.Then,they were applied to the analysis of hydroxyl nitro aromatic compounds,dopamine?DA?and permanganate?MnO₄^-?respectively.All of this expanding the application of MOGs in the analysis field.The specific research content is as follows:?1?Al-based metal-organic gels for selective fluorescence recognition of hydroxyl nitro aromatic compounds:Al-MOGs,which possesses blue fluorescence,have been developed by mix Hcptpy and Al³⁺under mild condition.The as-prepared Al-MOGs not only have multiple stimuli-responsive properties to ultrasound,shaking,heating,acids and bases,the fluorescent of Al-MOGs could also selective quenched by 4 kinds of hydroxyl nitro aromatic compounds in the 15 kinds of nitro aromatic compounds.Compared with p-nitrophenol?4-NP?,3,5-dinitrosalicylic acid?3,5-DNTSA?and 2,4-dinitrophenol?2,4-DNP?,picric acid?PA?has the lowest lowest unoccupied molecular orbital?LUMO?energy levels and inner filter effects?IFEs?.PA has the greatest degree of fluorescence quenching of the gel at the same concentration consequently.Thus,a new method for the selective detection of PA was established.?2?Cu?II?based metal-organic gels as a novel peroxidase mimic and used for colorimetric detection of DA:Based on the mimic enzyme property of Cu-MOGs,visual detection of DA was achieved by spectrophotometry.First,Cu-MOGs were freeze-dried to obtain Cu-MOXs and used for the next experiment.Cu-MOXs could catalyze the peroxidase substrate 3,3',5,5'-tetramethylbenzidine?TMB?to the oxidation state of TMB?oxTMB?by·OH radicals produced from H₂O₂and the TMB solution will turn blue.Then,the oxidation process of TMB will be confined when the DA was added into the mixed solution.Based on this,the colorimetry based on Cu-MOXs-TMB-H₂O₂ system for DA detection was established.And the linear range for DA was 0.5?M-20?M.The work expands the application of MOGs as an mimic enzyme material in analysis.?3?One-pot fabrication of AgNPs/MOGs for SERS detection of MnO₄^-:MOGs are prepared from organic small molecules and metal ions and can also be used to synthesize noble metal nanoparticles.Therefore,the coordination and reduction of hcptpy was used to Ag⁺in this experiment.A part of the Ag⁺was directly coordinated with Hcptpy,while another part of Ag⁺were reduced to AgNPs on the MOGs surface by the pyridine group in the structure of Hcptpy.Then,MOGs have high surface area and surface affinity to adsorb AgNPs at the surface and AgNPs/MOGs composites were obtained.Due to the high-density of AgNPs,which could generate Raman hot spots and greatly enhances the Raman signal of the Raman label,on the MOGs surface and the gelator as an endogenous Raman label,AgNPs/MOGs were used for surface-enhanced Raman scattering?SERS?.AgNPs/MOGs itself has a certain Raman signal.When a certain concentration of MnO₄^-is added,the Raman signal of AgNPs/MOGs is reduced due to the chemically etch of MnO₄^-on AgNPs.Based on this,the system establishes a simple,highly sensitive and selective SERS analysis method was used to detect MnO₄^-.In summary,we studied the Hcptpy-based MOGs and their composite materials,and successfully used in the analysis of hydroxyl nitro aromatic compounds,DA and permanganate.This article further enriches the application of MOGs in the application in analysis.