The Study On Design And Synthesis Of Novel Metal-organic Framework Based Catalysts And Catalytic Performance

With the development of the catalytic science,building an ideal environment-friendly catalyst is a hot topic in current research.However,there is still a great challenge for synthesis of heterogeneous catalysts with high catalytic activity.Recently,the combination of metal nanoparticles and metal organic framework?MOF?has been widely concerned by researchers.As a representative of heterogeneous catalysts,metal nanoparticles have high catalytic activity.However,the exposed metals are prone to agglomeration and inactivation.MOF has large specific surface area,unobstructed pore structure and large porosity,which can be used as the carrier to significantly improve the dispersion and loading of active components.In addition,due to the special skeleton structure of MOF,it can be used as sacrificial template,which can be heated at high temperature to obtain metal and carbon composites in situ.Therefore,our paper mainly research on the structure of the catalyst,including the size of metal nanoparticle and the interaction between active sites and carrier.The catalysts are characterized by N₂ physical adsorption,X-ray photoelectron energy spectrum,UV visible spectrum,transmission electron miscroscopy,scanning electron microscopy,Raman,inductively coupled plasma emission and hydrogen program heating and reduction.The coupling reaction of benzaldehyde,phenylacetylene,and piperidine and the catalytic properties of olefin hydrogenation were studied.The structure-activity relationship between the catalysts and the reaction performance was explored.The main research contents and results are as follows:?1?MOF-199 loaded with ultrafine Au nanoparticles was synthesized by microwave-assisted heating in one pot method.The effects of heating method,solvent ratio and amount of surfactant?PVP?on Au particles and loading were discussed in detail.As a result,the loading of Au?<2 nm?could be increased up to a level of 5.13%when microwave radiation was used as heating method,N,N-dimethylformamide?DMF?was selected as solvent,and 1000 mg PVP was added.Finally,Au/MOF-199 was applied to the performance evaluation of benzaldehyde,phenylacetylene and piperidine coupling reaction.It was found that all the catalysts showed excellent and similar catalytic performance,which indicated that high loading of Au/MOF-199 had better practical application significance.Among them,the values of TON and TOF of 5.13%Au/MOF-199 are 363 and 738 h^-1,respectively.Owing to the protective effect,the catalysts can be recycled for at least 5 times,while the catalytic activity is not significantly reduced and the skeleton is not damaged.In addition,hot filtration experiment verify that there is no active components loss,which was proved to be heterogeneous catalytic reaction.?2?PtCu alloy with different morphologies was synthesized by adjusting the addition of glycine under hydrothermal method.Then,PtCu alloy was used as template,Fe³⁺was used as oxidation etching agent,followed by the in-situ formation of MOF-199 on the surface of PtCu alloy to construct PtCu frame@MOF-199.The effects of heating method,the addition of Fe³⁺and PVP on the structure of catalysts are discussed.Finally,PtCu alloy and PtCu frame@MOF-199 with different morphologies were applied in the hydrogenation of 1-hexene.It was found that octahedral PtCu frame@MOF-199 showed the highest catalytic activity due to the more exposed active sites and the adsorb of hydrogenation by MOF-199,which promoted the reaction progress.Under the protection of MOF shell,the catalytic activity did not decrease significantly after 4 runs.In addition,the size-selective catalytic function of PtCu frame@MOF-199 was verified by using 1-hexene,cyclooctene and styrene as substrate.?3?First,microwave assisted heating was used to synthesize uniform nano-spherical Co-BTC.Then,Co-BTC was used as sacrificial template and heated at 400 ^oC,500 ^oC,600 ^oC,and 700 ^oC for 2 h to construct Co particles loaded on carbon with different structure and composition.XRD and Raman characterization showed that,with the increase of temperature,the degree of carbonization gradually increased,and the composition of the catalyst constantly changed.When the temperature increased to 700^oC,core-shell structure of Co@CoO_x was detected through TEM,HRTEM,and XPS characterization.When all the catalysts were used in 1,3-butadiene selective hydrogenation,it was found that the sample heated at 500 ^oC show the best catalytic activity.It can be run 30 h without serious loss activity under 60 ^oC.However,the sample heated at 700 ^oC exhibit highest selectivity of single olefin.The selectivity of single olefin could still reach 91%with almost total conversion of 1,3-butadiene.