Application Of Zirconium-based MOF Composites UiO-66-NH₂?Ti? In Photocatalytic Hydrogen Production

Metal organic framework?MOF?materials is a type of porous material.Its performance is easy to regulate and the structure changes are abundant.There is room for development in the collection and screening of fluids,electronic induction,optical and heterogeneous catalysis.Especially in the field of photocatalysis has shown good prospects.However,MOF materials have shortcomings such as the easy recombination of electron-hole pairs and poor water stability,the photocatalytic performance of MOF can still be improved.On the one hand,there have been reports of improving its performance by modifying nano rare-metal material;On the other hand,inspired by semiconductor photocatalysts,based on the semiconductor-like properties of MOF,by constructing MOF-MOF or MOF-semiconductor heterojunction can also effectively improve its photocatalytic performance.In this paper,two types of new composite materials were constructed using zirconium-based MOF replaced by titanium with platinum nanoparticles and g-C₃N₄ respectively.The performance and mechanism of photocatalytic hydrogen production were studied.Firstly,the zirconium-based MOF material,UiO-66-NH₂,was replaced with titanium.UiO-66-NH₂?Ti?containing different proportions of titanium was obtained.After that,two composite materials,Pt@UiO-66-NH₂?0.1Ti?and g-C₃N₄/UiO-66-NH₂?0.1Ti?,were prepared by compounding with g-C₃N₄ and platinum nanoparticles with the sample.The composite materials were tested and characterized by XPS,XRD,TEM,SEM,UV and PL.In the composite material Pt@UiO-66-NH₂?0.1Ti?,titanium is incorporated into the UiO-66-NH₂ framework,and platinum nanoparticles act as cocatalyst and modify inside.Titanium atoms partially replace zirconium atoms to form oxygen-bridged metal clusters,which facilitates the separation of electron-hole pairs,and the internal modification of platinum nanoparticles provides sufficient catalytically active sites.This improves the photocatalytic performance of the composite material.Under UV/visible light,the highest hydrogen yield of the composite material can reach 0.58 mmol h^-1 g^-1,which is about 3.4 times that of UiO-66-NH₂ under the same conditions.In the composite material g-C₃N₄/UiO-66-NH₂?0.1Ti?,titanium is incorporated into the UiO-66-NH₂ framework,and g-C₃N₄ is coated on the surface,forming a heterojunction with the MOF.As the content of g-C₃N₄ increases,the photocatalytic performance also increases.However,when the ratio exceeds 1:10,the performance starts to decline.By using 0.1g-C₃N₄/UiO-66-NH₂?0.1Ti?and adding excess platinum particles as co-catalyst under UV/visible light,H₂ production efficiency of0.1g-C₃N₄/UiO-66-NH₂?0.1Ti?can reach 43.5 mmol h^-1 g^-1,which is about 2.6 times that of UiO-66-NH₂ under the same conditions.