Preparation,Characterization And Catalytic Application Of MOF-74

Metal organic frameworks（MOFs）have emerged as a novel platform offering new promise for photocatalytic applications.MOF-74 has a one-dimensional hexagonal pore structure and"open"metal sites,as well as the tunability of organic ligands and metal ions,so it shows great potential in photocatalysis and electrocatalysis.Although many studies on the application of MOFs to photocatalysis have been reported,there were some problems,including low product yield and low stability,and the catalytic mechanism is still controversial.In this work,we reported a reversible and efficient mixed-metal MOF-74 catalyst（CoFe-MOF-74）for visible light-driven H₂generation,which can reach an activity of 28296μmol/g H₂ after 22 h.And the in-situ X-ray absorption spectroscopy was used to reveal the catalytic mechanism of the MOF in hydrogen evolution reaction.We showed that both Co and Fe centers in MOF-74 are the reversible active sites,and the accumulation of their reduced states is responsible for the observed induction period for H₂ generation.Moreover,we captured the key intermediate species formed when the reaction reaches equilibrium,which is featured by an elongated Co-O bond at the Co center and a more distorted octahedral geometry at the Fe center with respect to their original geometry.These results not only demonstrate the potential of MOF-74 as a single site catalyst for H₂ generation but also provide new insight into the catalytic mechanism for further development.In addition,for solving the current problem of inefficiency caused by the"lazy"reaction of oxygen evolution reaction（OER）in the electrocatalytic water splitting,CoFe-MOF-74 nanorod was synthesized for the electrocatalytic oxygen evolution reaction,which shows excellent electrocatalytic characteristics of 294 mV overpotential and 70 mV/dec Taffel slope,which is attributed to low electron transfer resistance lead to faster electron transfer process and a larger electrochemically active area.In summary,CoFe-MOF-74 is a potentially versatile catalyst material with good electrochemical and photocatalytic properties.