Near-infrared Photothermally Reinforced Ring-opening Reaction Catalyzed By Charge Transfer Complex@Polyoxometalate

Near-infrared photothermal catalysis is a new catalytic method that utilizes the photothermal effect to enhance chemical reactivity.Near-infrared light absorption in the low-energy region has been proven to be effective for light-to-heat conversion.Near-infrared photothermal conversion is a new way to utilize near-infrared light.However,the field of near-infrared photothermal catalysis is in the initial stage of development.There are many shortcomings in the field of near-infrared photothermal catalysis,such as limited photothermal materials,low near-infrared photothermal conversion efficiency,and poor catalytic effect.This brings opportunities for near-infrared photothermal catalysis.Polyoxometalates are inorganic nano-clusters,and the more negative charges on the surface can be electrostatically modified by organic molecules.Polyoxometalates have good electronic structure tunability,so they have good catalytic performance.At present,the reaction of polyoxometalates is limited to the traditional photocatalytic and thermocatalytic forms,and there are few reports in the field of near-infrared photothermal catalysis,which brings new possibilities for the application of polyoxometalates in near-infrared photothermal catalysis.In this paper,a series of detailed characterizations of the structure and corresponding photothermal catalytic properties of near-infrared photothermal catalysts were carried out,and its application in near-infrared photothermal catalysis was explored.First,the electron transfer complex was obtained after oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB）by ferric nitrate.Among them,TMB and TMB²⁺are paired,and there is aπ-πforce between them.We have demonstrated the formation and structure of the electron transfer complex by electron paramagnetic resonance,elemental analysis,thermogravimetry,infrared and ultraviolet spectra.Using Si W₉V₃polyoxometalates as the catalyst,the TMB_CT@Si W₉V₃ composite photothermal catalyst was prepared for the ring-opening reaction of styrene oxidation.The prepared complex exists as aggregates of about 100 nm in aqueous solution,the near-infrared photothermal conversion efficiency is as high as 47.7%,and it has good acid and alkali resistance and thermal stability.Second,its activity on the ring-opening reaction of styrene oxide was focused on,and the reaction process was studied in detail.By comparison,it was found that the conversion of styrene oxide by TMB_CT@Si W₉V₃ performed best under near-infrared photothermal catalysis,which may be due to the presence of metals V and W,which are favorable for the reaction as Lewis acid catalytic sites.The introduction of the photothermal effect enables the catalyst to open the ring of styrene oxide to generate the only product 2-methoxy-2-phenylethanol under normal pressure,with a selectivity as high as 100%.TMB_CT@Si W₉V₃ can still exhibit structural stability after the completion of the catalytic reaction.Therefore,through the supramolecular electrostatic interaction between functional electron transfer complexes and polyoxometalates,polyoxometalates complex-based near-infrared photothermal catalyst can be obtained under 808 nm near-infrared light.Thermally synergistically catalyzed ring-opening reactions.In this paper,the near-infrared photothermal catalytic system of polyoxometalates was established,and the ring-opening reaction of styrene oxide enhanced by near-infrared photothermal catalysis was realized.The direction of chemical catalysis provides new avenues.