Synthesis And Synergistic Catalysis Of Metal Nanoparticles/MOF-Based Composites

Metal-organic frameworks(MOFs),emerging as a relatively new class of crystalline porous materials formed by self-assembling of metal ions/metal clusters and organic ligands,attract extensive interest and exhibit a variety of applications,especially in catalysis due to their high surface area,structural diversity,and tailorability.The pore structure of MOFs can facilitate the transport of substrates/products and guarantee the accessibility of the catalytic active sites.Moreover,the uniform pore structure can be used for the screening of molecular size to improve the selectivity of the reaction.In addition,the well-defined and tailorable crystalline structures of MOFs make them to be an ideal platform for the establishment of clear structure-property relationships.1.Aniline and its derivatives are important chemical materials with the production of over 4 million tons every year.They are widely used in the synthesis of dyes,polymers,pesticides,medicines and various fine chemicals.The common route for their preparation is the reduction of the corresponding nitro derivatives in the presence of noble metal catalysts under H2 atmosphere.However,the hydrogenation in the presence of H2 typically requires high temperatures and/or H2 pressures.In this work,a Pd precursor was rationally introduced into MIL-101 via a double solvent approach followed by in situ reduction by ammonia borane(NH3BH3)to give the Pd@MIL-101 catalyst.The tiny Pd NPs of 3 nm in diameter are well confined inside the cavities of MIL-101.The obtained Pd@MIL-101 exhibited excellent catalytic performance in tandem dehydrogenation of NH3BH3 and reduction of nitro compounds.Notably,when NH3BH3 was replaced with H2 flow while other conditions remained,the reaction rate is 20 times slower than that of the above NH3BH3-engaged tandem process.Moreover,the method can be extended to the inexpensive CuNi@MIL-101 catalyst and the high catalytic performance can still be maintained.In this work,MNPs are active centers and MOFs behave as stabilizers for MNPs,which represents the simplest synergy between MNPs and MOFs.2.The hydrogenation of compounds with unsaturated bonds is a common transformation involved in many chemical processes.Tracditionally,hydrogenation reactions are usually carried out with hydride reagents(such as NaBH4,LiAlH4,and NH3BH3).However,hydride reagents are expensive,and their decomposition leads to by-products that are difficult to separate from the reaction system.Catalytic reduction with H2 obviously represents an attractive and more atom-economic alternative.However,employing H2 as a reductant to achieve the hydrogenation of unsaturated compounds usually requires high temperatures or/and pressures,which is disadvantageous in terms of environment,energy,cost and safety.We rationally grew a ZIF-8 shell on Pd nanocubes(NCs)to obtain Pd NCs@ZIF-8.The obtained Pd NCs@ZIF-8 composite realizes efficient and selective catalytic hydrogenation of olefins at room temperature under 1 atm H2 and light irradiation,by the integration of the plasmonic photothermal effect of Pd NC core and multiple roles of ZIF-8 shell:H2 enrichment,size-selectivity for different olefins as well as stabilization for Pd cores.This work represents the first attempt on coupling solar energy into catalytic reactions via integration of metal surface plasmon resonance effect with MOFs,which will exert their synergistic advantages and open up an avenue of utilizing solar energy instead of traditional heat to drive heterogeneous catalytic reactions.3.In recent years,a series of environmental problems(such as ocean acidification and global warming)caused by C02 have attracted wide attention.It is urgent to reduce the concentration of C02 in the atmosphere.Meanwhile,as a plentiful C1 resource,CO2 can be converted into various value-added products.The elimination of escalating CO2 in atmosphere based on C02 capture and conversion is very promising,particularly,the synthesis of cyclic carbonates via CO2 cycloaddition with epoxides.The present heterogeneous catalysts usually require moderately high temperatures to drive this reaction due to the inert nature of C02.The process is high energy-consuming,and therefore it is highly desired to utilize solar energy instead of additional heating for this reaction via the photothermal effect of catalysts.In this work,we have rationally fabricated a new type of hollow porous carbons(HPC),featuring well-dispersed dopants of nitrogen and single-atom Zn species,based on template-directed growth of hollow metal-organic framework precursor and subsequent pyrolysis.The optimized HPC-800 achieves efficient catalytic C02 cycloaddition with epoxides under light irradiation at ambient temperature,by taking advantage of single-atom Zn and uniform N active sites,high-efficiency photothermal conversion as well as the hierarchical pores in the carbon shell.This work represents not only the first attempt on introducing single atoms but also the first example of integration of photothermal effect into the endothermic CO2 cycloaddition conversion,which synergistically promote the catalytic process.We envision that the current fabrication strategy,on the basis of MOF precursors,to prepare single atom catalysts featuring significant photothermal effect will open an avenue to enhanced catalysis toward diverse reactions.