Research On High Performance OER Catalysts And Carbon-hydrogen Bond Oxidation Catalysts Based On Cobalt-based MOFs

Metal-organic frameworks（MOFs）are ordered porous coordination crystalline materials formed by the polymerization of metal nodes and organic ligands.They have high surface area,large pore size,easily adjustable structure and are widely used in chemical catalysis.In this paper,two sets of catalysts for oxygen evolution reaction and C-H bond oxidation reaction were prepared by using Co^Ⅱas the metal ion source.The first set of catalysts uses cobalt ions as the metal node to synthesize Co MOF-NH₂in situ on nickel foam by a two-step method,and then calcined in an argon atmosphere to obtain a porous sheet material Co₃O₄/NC.Co₃O₄/NC and several precursors were used to catalyze OER;in addition,Co-BPDC（BPDC=Biphthalic acid）was synthesized by a one-pot method,and it was used as the precursor to prepare small spur-shaped Co₃O₄@NC,which was also used for catalysis OER;The second group of catalysts used Zn^Ⅱand Co^Ⅱas mixed metal ion nodes and carboxyphenyl porphyrin as ligand to synthesize ultra-thin two-dimensional MOF,and used it for toluene catalytic oxidation reaction.This article specifically includes the following two aspects:（1）First,using cobalt chloride as a raw material,a sheet-like Co₃（OH）₂Cl material was grown in situ on foamed nickel with good conductivity by hydrothermal method.Then through ligand conversion,the nitrogen-containing organic ligand o-aminoterephthalic acid was introduced to synthesize the lamellar Co MOF-NH₂and calcined under argon atmosphere,and finally the nano-layered material Co₃O₄/NC with special pore structure was obtained.Using Co₃O₄/NC directly as a working electrode to catalyze OER,current densities of 10 m A/cm²and 100 m A/cm²can be achieved at ultra-low overpotentials of 235 m V and 264 m V.In addition,using cobalt nitrate and biphthalic acid as raw materials,a one-pot method was used to stir and react in an autoclave to synthesize MOF intermediates and calcined at 500°C for2 hours to obtain small spines of Co₃O₄@NC.Co₃O₄@NC powder is coated on the glassy carbon electrode as a working electrode to catalyze OER,and current densities of 10 m A/cm²and 100 m A/cm²can be achieved at 255 m V and 290 m V.Although it is not comparable to the catalytic activity of Co₃O₄/NC,the catalytic effect as a powdered catalyst（without foamed nickel as a substrate）is also comparable to that of a commercial catalyst（Ir O₂）.（2）Through C-H oxidation,simple hydrocarbon compounds can be converted into higher-value oxygenated products.As a simple benzyl compound,toluene is catalyzed and oxidized into chemical products such as aldehydes,alcohols or acids with higher value,which is a very important research topic.Here,Zn ^IIand Co ^IIare used as mixed inorganic nodes,and cobalt porphyrin is used as organic ligand to successfully prepare a lamellar two-dimensional MOF catalyst.Its lamellar two-dimensional structure is conducive to exposing more metal active sites,and the insertion of zinc ions into cobalt ions is also conducive to dispersing cobalt ions,so that cobalt ion active centers expose more active sites.In addition,the structure of MOF can anchor the catalytically active cobalt porphyrins so that they cannot reunite with each other,so that the active sites on the cobalt porphyrins can be fully utilized.These factors are all conducive to the progress of the catalytic oxidation reaction.It is used in the toluene oxidation reaction,with cumene hydrogen peroxide as the oxidant,under the optimal process conditions,a toluene conversion rate of74.7%and a benzaldehyde selectivity of 84.3%can be achieved.