Selective Oxidation Of Aromatic Alcohols Over Post-Modified NH₂-MIL-125（Ti） Catalysts Under Visible Light

Aromatic aldehydes are important fine chemical intermediate, which have been commonly used in the synthesis of drugs, spices and so on. These aromatic aldehydes in the industrial manufacture are traditionally produced by an oxidation or chlorization-hydrolysis method, eventually leading to a high input and serious environment pollution. As a kind of green synthesis methods, photocatalytic oxidation technologies have gained increasing concern. However, semiconductor photocatalysts have shown the less utilization of visible light and a poor selectivity in the oxidation of aromatic alcohols to the corresponding aldehydes. Therefore, the development of new photocatalytic materials is considered as a key step for the application of the photocatalytic oxidation technologies. The flouring development of metal-organic frameworks (MOFs) in terms of research and application in recent years brings new hope for research and development in photocatalyst with high selectivities and activities.In this thesis, the photocatalysts were synthesized via post-modification of the amino-functionalized Ti based metal-organic framework, the so-called NH2-MIL-125(Ti) with either 2-pyridaldehyde (2-PA) or metallic Ni. These synthesized catalysts were characterized by several techniques such as XRD, TEM, UV-vis and photocurrent test etc. Afterwards, these catalysts were applied to the selective oxidation of some aromatic alcohols under visible light to gain their photocatalytic properties. The obtained main results are summarized as follows:1. The 2PA-modified photocatalyst, the so-called 2-PA@NH2-MIL-125(Ti), shows an enhanced absorption capacity in a visible-light region, compared with NH2-MIL-125(Ti). Under visible light,2-PA@NH2-MIL-125(Ti) can selectively catalyzes the oxidation of benzyl alcohol to benzaldehyde and its photocatalytic activity is significantly improved, compared with NH2-MIL-125(Ti).2. The metallic Ni-modified photocatalyst, the so-called 1 wt.% Ni@NH2-MIL-125(Ti), also shows an enhanced activity in the selective oxidation of some aromatic alcohols to the corresponding aldehydes under visible light, compared with NH2-MIL-125(Ti). This could be due to the fact that the doped metallic Ni nanoparticles in the MOF beneficial not only to visible-light harvesting but also to the excitation and transformation of the photogenerated electrons in the photocatalytic oxidation reaction.Novelty of the thesis research:The post-modification of 2-PA or metallic Ni in NH2-MIL-125(Ti) can enhance their photocatalytic activity in the selective oxidation of some aromatic alcohols under visible light. Therefore, this work also provides some guidance in the synthesis of visible-light induced MOF-based photocatalysts and highlights the potential of MOFs in the application of organic syntheses.