Preparation And Photocatalytic H₂O₂ Production Properties Of Metal Organic Frameworks NH₂-MIL-68 Composites

As an ideal photocatalyst,metal organic framework?MOFs?has been widely used in the field of photocatalytic hydrogen production and degradation,and has good performance.However,there are few reports in the field of photocatalytic H₂O₂ production.Therefore,in this paper,we first explored the photocatalytic H₂O₂ production reaction using MOFs as photocatalyst and H2 O as the sole reactant.MOFs photocatalysts exhibit excellent photocatalytic hydrogen peroxide production performance under visible light??>400 nm?and without oxygen input.Modified with some functional groups in the structure of MOFs organic ligands,the light absorption edge can be effectively extended to the visible light region by introducing amino groups,broadening the spectral response range of the corresponding MOFs to enhance light absorption efficiency,which is conducive to photogenerated electron excitation and reduces the recombination rate of photogenerated electrons and holes,improves the utilization efficiency of sunlight and enhances photocatalytic activity.First of all,the selected NH₂-MIL-68?In?material has a more suitable band gap width and energy band position,which makes NH₂-MIL-68?In?without co-catalyst has good photocatalytic performance for H₂O₂ production.In the experiment,it is found that the heating time directly affects the photocatalytic performance of NH₂-MIL-68?In?,With the increase of heating time,the performance of H₂O₂ production first increases to the highest and then decreases,and then the best reaction time is determined.The NH₂-MIL-68?In?,heated by steam heating for 4 hours has the best photocatalytic performance of producing H₂O₂,and the photocatalytic speed is 252.5 mol·g^-1·h^-1.TEM and SEM tests showed that NH₂-MIL-68?In?was polycrystalline,which greatly increased the contact area with reactants.This is also the reason why NH₂-MIL-68?In?has good photocatalytic activity.The ESR test showed that the main active species was ·OH and corresponding catalytic mechanism was proposed.Secondly,g-C₃N₄/NH₂-MIL-68?Al?composite was synthesized by a simple dynamic solvothermal method.G-C₃N₄ can effectively extend the visible light range of wide band gap semiconductor NH₂-MIL-68?Al?.The combination of g-C₃N₄ and NH₂-MIL-68?Al?can effectively increase the utilization rate of visible light,and the synergy between the two can effectively improve the charge separation efficiency and greatly improve the photocatalytic activity.With the increase of the amount of g-C₃N₄,the performance of photocatalytic water to produce H₂O₂ is gradually improved.When the mass ratio is 1:1,the composite achieves the best performance of hydrogen peroxide production,which is 6.48 times and 6.98 times of g-C₃N₄ and NH₂-MIL-68?Al?,respectively.The ESR test showed that the main active species were ·OH and ·O₂^-,and the possible double channel photocatalytic mechanism was proposed.