MOFs-derived Metal-acid-base Multifunctional Catalysts And Their Catalytic Conversion Of Cellulose Into Low-carbon Diols

With gradual fossil resources depletion,the conversion of renewable biomass into high value-added chemicals has attracted great attention.As the most abundant biomass resource,cellulose is highly valued due to its low cost,large reserves,and carbon neutrality.Cellulose can be directly converted into low-carbon diols（such as 1,2-propanediol,ethylene glycol,etc.）through catalysis,thereby achieving high atom economy and high energy efficiency,which is of great significance for sustainable development.The direct preparation of low-carbon diols from cellulose involves multiple steps hydrolysis,isomerization,retro-aldol condensation,hydrogenation,dehydration,and the design of multi-active site catalysts has become the focus of research.In this paper,combined with the multi-step characteristics of the reaction,a new type of multi-active site catalyst was prepared by using metal-organic frameworks（MOFs）as precursors through precursor calcination,solid-state transformation,and active site modulation and structural design.The relationship between reaction performance and catalyst structure,active site composition,and content is deeply studied.The details are as follows:The Zn-BTC and ZIF-8 MOFs precursors were mixed,and the microrods were converted into nanorods using an acid-base etching strategy.After solid-state conversion,sulfonation treatment,and metal loading treatment,a metal-acid-base multi-active nanorod catalyst（Ru/MNCR-SO₃H-1.0）was prepared.By changing the content of ZIF-8,the microrods can be nanosized to different degrees,and the content of metal/acid/base multi-active sites and physical texture properties can be simultaneously regulated.The Ru/MNCR-SO₃H-1.0 has a high specific surface area（1088 m²/g）and contains optimal metal,acid,and base contents.The synergy of the multiple active sites of the catalyst promotes the equilibrium of the multi-step reaction of cellulose hydrolysis hydrogenolysis,thereby improving the reaction performance of cellulose to prepare low-carbon glycols.A Ru-SO₃H active site separation“yolk-shell”catalyst（Ru/NC@void@MC-SO₃H）was prepared by a layer-by-layer assembly strategy.The inner core and outer shell of the catalyst are MOFs based in-situ encapsulated metallic Ru-derived N-doped carbon and carbon shell containing-SO₃H group,respectively.The catalyst can not only realize multi-functional integration but also separate active sites.The Ru/NC@void@MC-SO₃H catalyst was used in the reaction of cellulose to diols,the yields of main products 1,2-PG and EG reached 38.0%and 12.0%,and the total low-carbon diols yield was 505.27mol/h·g _Ru.The catalyst possesses spatially separated Ru-SO₃H sites while possessing excellent mesoporosity,which provides a designated diffusion pathway for cellulose hydrolysis hydrogenolysis.