| Metal-organic frameworks(MOFs) is a kind of hybrid materials formed by self-assembly with organic ligands and metal ions or clusters. It has been successfully applied in storage gas, adsorption and separation, catalysis, magnetic materials and other fields, because its porous, high surface area, adjustable structure and unsaturated metal sites properties. However, large steric effect of the complicated organic chain has limited electron transfer, resulted in poor conductivity, so it is not widely used in electrochemical sensors. We improve the deficiencies of MOFs by combine the metal-organic frameworks and other materials together, the prepared electrochemical sensor can detect trace substances in real samples effectively, the main research contents are as follows:Chapter 2 Cu3(BTC)2/β-CD composite electrode for simultaneous quantification of guanine and adenineIn this work, a novel chemically modified electrode is constructed based on metal-organic frameworks and β-cyclodextrin (Cu3(BTC)2/β3-CD, BTC=benzene-1,3,5-tricarboxylate) composite material. The electrode was used for simultaneous determination of guanine and adenine and exhibited sensitive responses to guanine and adenine oxidation due to the n-n stacking interaction of Cu3(BTC)2 and the inclusion behavior of β-CD. The analytical performance was assessed with respect to the supporting electrolyte and its pH, accumulation time and accumulation potential. Under optimal conditions, linear calibration ranges for both guanine and adenine were from 0.1-1.0 μmol·L-1 to 1.0-10 μmol·L-1, and detection limits were found to be 0.052 μmol·L-1 and 0.028 μmol·L-1, respectively. The proposed sensor showed advantages of high sensitivity, simple sample preparation protocol and good reproducibility. Finally, the practical application of the proposed sensor has been performed for the determination of guanine and adenine in real samples with satisfactory results.Chapter 3 AuNPs/MMPF-6 composite modified electrode for detection of hydroxylamineGold nanoparticles supported on metal-metalloporphyrin frameworks, AuNPs/MMPF-6, were prepared by a layer-by-layer assembly technique through electrostatic adsorption. The composites were characterized by powder X-ray diffraction, zeta potential, transmission electron microscopy, and electrochemical impedance spectroscopy, and showed a pair of direct redox peaks of the Fe(III)TCPP/Fe(II)TCPP redox couple. AuNPs/MMPF-6 based electrochemical sensor exhibits a distinctly higher electrocatalytic activity for the oxidation of hydroxylamine due to the synergic effect of the highly dispersed gold metal nanoparticles and metal-metalloporphyrin matrix. The voltammetric current response exhibits two linear dynamic ranges 0.01-1.0μmol·L-1 and 1.0-20.0 μmol·L-1, and the detection limit was as low as 0.004 μmol·L-1 at a signal-to-noise ratio of 3. Moreover, the sensor exhibits high reproducibility and stability with a relative standard deviation of 2.2%. The method provides a facile way to expand the potential applications of MOFs based composites in analysis.Chapter 4 UiO-66-NH2/TiO2 composite modified electrode for the determination of chlorogenic acidIn this work, amino functionalized metal organic framework material(UiO-66-NH2)and titanium dioxide(TiO2)composite were synthesized, and prepared a new sensor for the detection of chlorogenic acid. The composites were characterized by powder X-ray diffraction, Fourier infrared spectroscopy, N2 adsorption isotherms, scanning electron microscopy, energy spectrum, transmission electron microscopy, the results showed that UiO-66-NH2 and TiO2 can combinate together according to the heterogeneous nucleation effect. The electrochemical sensor prepared by UiO-66-NH2/TiO2 composite showed a good response to the determination of chlorogenic acid. Under the optimum operating conditions, the oxidation peak current was linear with the concentration of chlorogenic acid in the range of 0.01-1.0 μmol·L-1 and 1.0-13.0 μmol·L-1 with a linear correlation coefficients were 0.9993 and 0.9997, respectively. The detection limit of 0.007 μmol·L-1, and the relative standard deviation of 9 successive scans was 2.67% for 1.0 μmol·L-1 chlorogenic acid. The content of chlorogenic acid in the actual sample was determined, and the obtained recovery were satisfactory.
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