Construction Of Hydrotalcite Based Composite Visible Light Photocatalyst And Its Application In Cross Dehydrogenation Coupling Reaction

As a green and clean energy,visible light has been widely used in various organic synthesis photocatalysis.Transition metal visible light photocatalysts have been gradually replaced by organic dye visible light photocatalysts in certain fields due to their high price and scarcity of precious metals.Compared with transition metal visible light photocatalysts,organic dye visible light photocatalysts are cheap and easy to prepare.Synthetic chemists have realized the cross dehydrogenation coupling reaction(CDC reaction)between N-aryl tetrahydroisoquinoline and nitroalkanes using organic dye visible light photocatalyst.CDC reaction reduces the steps of synthesis;improves atomic utilization and reduces the formation of by-products.Relevant research has attracted many attentions in recent years.Tetrahydroisoquinoline compounds are ubiquitous in nature and have high research value in the fields of biology and medicine.The synthesis of tetrahydroisoquinoline derivatives by CDC reaction fits the concept of green chemistry.However,homogeneous organic dye visible light photocatalysts are usually difficult to separate,recycle and reuse from the reaction system,which is not in line with green chemistry.Therefore,chemists have been looking for a recyclable system based on organic dye visible light photocatalysts.Hydrotalcites,also known as Layered double hydroxides(LDH),have special host guest layered structure,excellent adsorption performance,ion exchange performance,catalytic performance,and guest protection of interlayer anions.Based on these properties,in this study,a three-dimensional nano flower LDH was prepared by hydrothermal method with urea as alkaline agent and sodium dodecyl sulfate(SDS)as template.The organic dye visible light photocatalyst Rose Bengal(RB)was intercalated in the layer of a three-dimensional LDH.Compared with the traditional two-dimensional nano flake LDH,the intercalation effect between three-dimensional LDH and RB is enhanced,and the protection of interlayer RB is further strengthened.LDH@RB Nano materials show excellent catalytic performance and recycling performance in CDC reaction of N-aryltetrahydroisoquinoline and nitromethane.However,the separation and recovery of LDH nano composites is very cumbersome.Based on the good anchoring effect and biological viscosity of polydopamine(PDA)on metal ions,we use PDA to modify the green material cotton cloth and use the hydrothermal method to load the three-dimensional LDH on the PDA cotton cloth and carry out supramolecular assembly with RB to prepare LDH/ RB@PDA Cloth composite.This novel composite catalyst showed excellent catalytic performance in the CDC reaction of N-aryltetrahydroisoquinoline with nitromethane.In this paper,two composite visible light photocatalysts with high loading capacity for organic dye visible light photocatalysts were prepared based on LDH materials,and successfully catalyzed the CDC reaction of N-phenyltetrahydroisoquinoline and nitromethane.Both showed excellent catalytic and recyclable performance,which provides a new concept for the design of efficient and stable LDH based composite visible light photocatalysts and has certain theoretical significance and practical application potentials.