Photothermal Catalytic Ullmann Coupling Over Supported Copper Nanoparticles

Ullmann coupling of phenols and aryl halides to construct C-O bond is well known as an important named reaction in organic chemistry.It is an effective route to convert phenol and aryl halide wastes into high value-added chemicals.However,the conventional Ullmann coupling requires harsh reaction conditions such as high temperature,excessive copper powder catalyst,addition of ligands etc.Therefore,it is great significance to explore an efficient catalytic process for Ullmann reaction under mild conditions.In recent years,“green” organic synthesis with solar energy has attracted many attentions due to the worsening environmental pollution and energy crisis.UV light only accounts for 4% of solar spectrum and visible-light takes 43%.Thus,the development of photocatalysts that response to visible-light is critically important to promote the utilization of solar energy.As earth abundant and low-cost material,copper becomes a promising photocatalyt since its nanostructure could strongly absorb visible-light due to the unique local surface plasmon resonance(LSPR)effect.The aim of this work is to develop a green and efficient route for Ullmann coupling reaction by utilizing the LSPR effect of copper nanostructures.The specific research content is as follows:1?Copper nanoparticles(Cu NPs)loaded carbon nanotubes(CNTs)were prepared by impregnation-reduction method and were characterized by various techniques such as XRD,XPS,UV-Vis and HRTEM.The results showed that Cu NPs mainly existed in the zero-valent state with an average particle size of approximately 9 nm and an obvious LSPR absorption peak at 580 nm;2?The prepared samples were utilized as photocatalyst for Ullmann coupling of phenol and aryl halide under visible-light irradiation.We investigated the influence of copper loading,particle size,reaction time,reaction temperature,light intensity and wavelength on the reaction.The optimized reaction conditions was obtained and control experiments were designed to investigate the reaction mechanism.It was found that the visible-light irradiation and light-excited Cu NPs could inhibit the degradation of phenol on CNTs,in turn promoting the cross-coupling of phenol and aryl halide.At the same time,the influence of different supports on the reaction activity were investigated.The results showed that CNTs exhibited excellent capability for light absorption and light-to-heat conversion as well as superior adsorption capability for both reactants,thus enhancing the yield of diaryl ether;3?To construct a sustainable economic system,CNTs derived from plastic wastes were used as supports.The photocatalyst achieved excellent activity when directly utilizing CNTs from various plastic wastes as supports,similar with commercial CNTs.This process at some extent fulfils the conversion of waste to value-added chemicals with solar energy.