Synthesis Of Multimetallic-ZIFs Derivatives And Their Catalytic Performance In Styrene Conversio

As one of very classic metal-organic frameworks（MOFs）,ZIFs has the similar special structure to the zeolite molecular sieve,and the excellent properties from MOF itself,such as high surface area,high thermal stability（300℃）and uniform micropore structure.After the simple pyrolysis of ZIFs at high temperature template,their derived materials can not only maintain the morphology,size,structure and advantages of the parent ZIFs,but also expose more metal active sites and greatly improve the thermal stability and acid-base stability.Hence it has attracted widespread attention in the field of catalysis.In this paper,we choose ZIFs as a template to form composite carbon materials for organocatalytic reactions.We first in situ grow MCo-ZIFs particles with matrix materials,and then pyrolysis to obtain carbon-based composites for photothermal epoxidation of styrene.Subsequently,four metallic ZIFs materials with different morphologies are designed and synthesized.Their corresponding derivatives are investigated in the tandem reaction of NH₃BH₃ dehydrogenation and olefin reduction.The results obtained are as follows:1.In recent years,metal-organic frameworks as precursors have been widely reported for obtaining various porous materials.However,improving the limited MOF types and monofunctional active site of MOF-derived catalysts remain to be a great challenge.In this first work,bimetallic MOFs,MCo-ZIFs stabilized by graphitized carbon nitride（g-C₃N₄）and their pyrolytic Mx Co₃O₄/g-C₃N₄ hybrids（M=Zn,Cu,Fe,Ni）have been designedly synthesized.The obtained hybrids display synergistic photothermal effect from both Mx Co₃O₄ and g-C₃N₄ under visible light irradiation.Significantly,the solution temperature can be heated from room temperature（20°C）to66°C after 40 min irradiation in present of hybrids.Benefiting from this point,the catalytic activity of Mx Co₃O₄/g-C₃N₄ exceeds those of most reported catalysts under mild reaction conditions,even some precious metal catalysts.The optimal Znx Co₃O₄/g-C₃N₄ catalyst realizes 96%conversion and 75%selectivity toward styrene oxide within20 min.Furthermore,the Cux Co₃O₄/g-C₃N₄ could achieve up to 89%selectivity toward styrene oxide.To our knowledge,this is the first report about the novel photothermal effect of ZIFs-derived metal oxides.2.In a second work of this paper,four kinds of morphology of ZIFs materials are designedly synthesized by adjusting the metal proportion and adding different surfactants.In addition,the derived Cu Co Ni@C is finally obtained via simple gradient temperature calcination.Its catalytic performance has been evaluated by the tandem reaction of NH₃BH₃ dehydrogenation and olefin reduction.The excellent catalytic activity exceeds those of most catalysts previously reported.This is mainly due to the small particle,dispersed metal active sites and the multi-metal synergy effect.In this paper,Zn Cu Co Ni-ZIFs are successfully synthesized,which provides novel ideas and guidance for the synthesis of other polymetallic MOFs.Furthermore,the catalyst has higher stability relative to MOFs,which is valued for industrial applications.