| In recent years,the combination of metal-organic frameworks(MOFs)and metal nanoparticles(MNP)to form core-shell material(MNP@MOFs)has become a new research hotspot in the field of chemistry.Because MOFs have the advantages of adjustable pore structure,good stability,and high specific surface area,combined with the unique properties of metals in catalysis and surface-enhanced Raman spectroscopy(SERS),MNP@MOFs has a wide range of applications in gas adsorption,Raman detection,heterogeneous catalysis,and other fields.However,there are certain deficiencies in the research of composites composed of metal nanoparticles and MOFs,including the construction and application of the composite in diverse fields.At present,the preparation methods of various core-shell nanoparticles are largely difficult to regulating the morphology and shell thickness,which greatly limits the performance.Herein,we developed two strategies for preparation of MNP@MOFs nanoparticles and obtained Au@ZIF-8 and Au@Pd@MIL-100(Fe)nanoparticles with different structures and morphologies.According to the different properties,the former was applied to the detection of various VOCs gas,and the latter was used in studying catalytic reaction with SERS technology.The details are as follows:1.In the preparation of Au@ZIF-8 nanoparticles,Au@ZIF-8 nanoparticles with single and multi-core structures can be obtained by controlling the concentration of the precursor in the solution.Under a certain concentration,the amount of precursor in the solution was controlled to adjust the shell thickness of the single-core Au@ZIF-8 nanoparticles precisely.The SEM,TEM,UV-vis,and XRD were used to characterize the morphology and physicochemical properties of Au@ZIF-8.Subsequently,the nanoparticles with different structures were prepared as SERS substrates.It was confirmed that Au@ZIF-8(3 nm)had a good SERS performance after being characterized by Raman spectroscopy.Finally,toluene gas adsorbed in Au@ZIF-8(3 nm)nanoparticles was detected,and the adsorption and desorption processes of toluene gas were characterized with in-situ SERS technology.The whole changing process of toluene gas was analyzed from adsorption,saturation,to desorption.In addition,toluene,ethylbenzene,chlorobenzene,and other VOC gas were also tested by Au@ZIF-8(3 nm)in order to analyze the universality of nanoparticles for VOCs gas detection.The above results confirmed the universality of MNP@MOFs composite in different VOCs gas testing.2.The Au@MIL-100(Fe)core-shell nanoparticles were obtained via the method of layer-by-layer coating,in which the shell thickness of MIL-100(Fe)was controllable and adjustable(at 3 nm or even thicker).The method was successfully applied to Au@Pd nanoparticles,and the Au@Pd@MIL-100(Fe)core-shell nanoparticles with different Pd layer thicknesses were synthesized.Then,p-nitrothiophenol(PNTP)was used as the probe molecule to test the SERS performance of nanoparticles,and the PNTP hydrogenation performance of Au@Pd@MIL-100(Fe)nanoparticles was studied by using in-situ SERS technology.The results showed that the SERS performance was gradually weakened with the increase of the Pd layer thickness,while the catalytic performance was greatly improved.Finally,the effects of Pd and MIL-100(Fe)on the PNTP hydrogenation reaction were analyzed by using Au@Pd1/4 and Au@Pd1/4@MIL100(Fe)nanoparticles.The experimental data indicated that the hydrogenation of PNTP was mainly dependent on the decomposition of H2 by Pd,while the MIL-100(Fe)in the shell could hinder the coupling between PNTP molecules and effectively decrease the generation of p,p’-dimercaptoazobenzene(DMAB)molecules as a by-product.This part illustrated that the multifunctional core-shell nanoparticle can regulate the products in the catalytic reaction. |
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