Amino-modified MOFs And Their Derived Nanomaterials As Effective Photocatalysts For Coupling Of Amines To Imines

Developing green and efficient organic synthesis process is the main direction for chemistry in the future.Heterogeneous photocatalysis for selective organic transformations has attracted great interest from scholars,not only because it's easy to separate from the reaction system,but also consists of its other special advantages such as mild reaction conditions,avoiding side reactions and meeting the requirements of green chemistry.The property of the photocatalyst is the most important element which influencing the photocatalytic efficiency.Metal-organic frameworks?MOFs?,which featuring semiconductor-like behavior because the organic ligands can serve as antennae to harvest light and energy transfer processes are always applied,has brought new hope for developing classes of pholocatalyst due to their well-defined and tailorable porous structures,high surface areas,etc.Meanwhile,the reason why the number of MOFs as an ideal templates for other porous materials has been growing fast is that the obtained materials not only maintained the structural characteristics of the parent MOFs,such as large surface area and greatly dispersed active sites,but also overcome the defect of collapse of some MOFs framework structure,which is important for photocatalysis.Taking into account all the above mentioned,in this paper,amino-modified MOFs and their derivatives were synthesized and applied as effective photocatalysts for the reaction of amines to imines,the internal relationship between the structure of photocatalysts and photocatalytic efficiency were further studied.The main results of this paper are as follows:1.UiO-66-NH₂ was prepared by a facile one-pot solvothermal method.The morphology,structure,specific surface area and optical properties of UiO-66-NH₂were characterized by XRD,SEM,FI-IR,XPS,BET and UV-vis DRS analysis.The results showed that the product could be detected not only in air but also in anaerobic conditions,which burst out of the shackles of the reported conditions previously.A series of experiments for the catching of the active species were performed,and the possible photocatalytic mechanism for amines to imines was proposed.The study highlighted the further understanding of the mechanism of photooxidation coupling of amines.2.Hierarchical In₂S₃ nanotubes were prepared by NH₂-MIL-68?In?and sulfur sources as precursors,which maintained the skeleton of NH₂-MIL-68?In?.The structure,morphology and optical properties of hierarchical In₂S₃ nanotubes were characterized by XRD,FI-IR,SEM,TEM,UV-vis DRS,PL and BET analysis.The results showed that the In₂S₃ with the mother framework of MOFs had higher catalytic activity than the In₂S₃ prepared by direct hydrothermal method,and hierarchical In₂S₃ nanotubes with smaller size of building blocks had higher catalytic activity than hierarchical In₂S₃ nanotubes with bigger size of building blocks.The study highlighted the potential strategy to design the size-reponsive building blocks of hierarchical structures and provided a new idea for developing the types of MOFs-based materials.3.Following the results of the second part,in order to improve the catalytic activity of In₂S₃ nanotubes with bigger size of building blocks,a cation exchange method was used to synthesize hierarchical In₂S₃/CdIn₂S₄ heterostructured composites.The structure,morphology and optical properties of the catalyst were characterized by XRD,SEM,TEM,HRTEM,UV-vis DRS and PL analysis.The results showed that the existence of heterojunction could minimized the recombination efficiency of photogenerated electron-hole pairs,which made the In₂S₃/CdIn₂S₄ show superior catalytic activity for the transformations of amines to imines.In this system,the oxidative coupling of benzylamine was still unaffected by oxygen.