Preparation Of Core-shell-structured Organic Frameworks Composite And Its Application In Electrochemical Sensor

As a new class of organic porous polymers,metal organic frameworks(MOFs)and covalent organic frameworks(COFs)are attracting tremdous attention due to their large surface area,high porosity,flexible functionality,and so on.Although both MOFs and COFs exhibit great performance advantages in various applications,the poor conductivity as well as limited catalytic activity has restained their application in electrochemical sensors.Against such backdrop,core-shell structures based on MOFs or COFs have stimulated much research interest because of their appealing topologies and predominant chemical performances.In this paper,core-shell-structured MOFs or COFs composite with enhanced conductivity as well as electrocatativity were synthesized and then applied to construct electrochemical sensors.The main contents are as follows:Chapter 2 A novel electrochemical sensor based on core-shell-structured metal-organic frameworks:the outstanding analytical performance towards chlorogenic acidIn this paper,a superparamagnetic Fe3O4 core encapsulated into a metal-organic framework shell,Fe3O4@MIL-100(Fe),was successfully synthesized taking advantage of layer-to-layer method.transmission electron microscopy(TEM),powder X-ray diffraction(XRD),fourier transform infrared spectroscopy(FTIR)and N2 adsorption/desorption isotherms were conducted to characterize the successful formation of core-shell-sturctured Fe3O4@MIL-100(Fe).Then,the synthesized material was firstly used to fabricate a novel electrochemical sensor for chlorogenic acid(CGA)detection.Under the optimal conditions,this electrochemical sensor can detect CGA quantitatively in the range of 0.1-10.0 μmol L-1 and 10.0-460 μmol L-1.The limit of detection(LOD)can be as low as 0.05 μmol L-1.Considering there are little common interfering materials,this novel chlorogenic acid sensor was further applied in real samples to detect the content of CGA.Chapter 3 Integrating polythiophene derivates to PCN-222(Fe)for electrocatalytic sensing of L-dopaPorphyrinic metal organic frameworks(porph-MOFs)are attracting attention due to the redox activity in the porphyrin subunit.Herein,we report the design of a novel core-shell structure hybrid material with a sea-cucumber morphology,namely PMeTh,containing the poly(3-methythiophene)conducting polymer coated on the surface of iron-based porph-MOFs PCN-222(Fe)via in-situ oxidative chemical polymerization.The porous PCN-222(Fe)serves as the electrocatalytic sites,while the poly(3-methythiophene)conducting polymer functions as the charge collector to facilitate the charge transport to the redox active sites.The resulting PMeTh composite demonstrates an excellent electrochemical response towards the levodopa detection.The sensitivity towards the L-dopa detection is estimated to be 1.868 μA μM-1 cm-2 in the linear concentration of 0.05-7.0 μmol L-1 and 0.778 μA μM-1 cm-2 in the linear concentration of 7.00-100 μmol L-1,respectively.Additionally,the levodopa sensor exhibits a low detection limit of 2 nmol L-1 as well as excellent stability after 120 cycles in 10 μmol L-1 levodopa.The feasibility of this novel L-dopa sensor was evaluated in human urine samples by standard addition.The satisfactory recoveries were in the range of 97.0-105.5%with the RSD value lower than 4.4%.The method of intergrating porph-MOFs and conducting polymers can efficiently expand the porph-MOFs based composites in bioanalysis.Chapter 4 Construction of Co3O4@TAPB-DMTP-COF composites for the enhancement of electrochemical properties towards TBHQHere,a monomer-mediated in situ growth strategy was developed for the controllable construction of Co3O4@TAPB-DMTP-COF composite by using Co3O4 as the core and TAPB-DMTP-COF as the tunable shell.Such a core-shell-type composite exhibits uniform size,regular aperture with high surface area,and ultrahigh effective surface area.Additionally,the Co3O4@TAPB-DMTP-COF based sensor is demonstrated sensitive and selective to tertbutylhydroquinone(TBHQ).Under optimized experimental conditions,the sensor can detect TBHQ over two linear dynamic ranges(0.05-1.0 μmol L-1 and 1.0-400μmol L-1)with an ultra-low detection limit(LOD)of 0.02 μmol L-1.The highest sensitivity is calculated to be 0.4388 μA μM-1 cm-2 at the first interval.What’s more,the feasibility of the established sensor is validated by standard addition method.All above results point that the Co3O4@TAPB-DMTP-COF/GCE sensor is capable to detect TBHQ in real samples.