Reaction And Mechanism Of Photocatalytic Oxidation Of Alcohols With TiO₂ Nanosheets

In the 21 st century,oil,natural gas and coal and other resources are facing depletion,and the environmental problems caused by the production and utilization of fossil fuels were becoming increasingly prominent.Therefore,the reduction of fossil energy consumption and the development of renewable clean energy are imperative.Among them,the green clean photocatalytic organic synthesis has aroused great concern in the field of chemistry and chemical industry.Photocatalytic organic synthesis is the use of renewable raw materials or energy,in the non-toxic,harmless conditions to achieve efficient,clean atomic economy and low energy consumption of the chemical reaction process,from the source to reduce and eliminate industrial production of environmental pollution,the atoms of the reactants are all converted to the desired product.However,due to the low efficiency of photocatalytic organic synthesis reaction,it is still impossible to realize the industrial production and application.In view of the above background,this dissertation aims to improve the efficiency of photocatalytic organic synthesis.From the point of view of molecular reaction design and catalyst design,we can use the cheap and simple chemicals to synthesis complex chemical with a high selectivity.Specific work and conclusions are as follows:?1?During the thermal catalytic reaction,pinacol is produced by acetone as a raw material through the classical McMurry reaction.Recently,our group found that isopropanol in the aqueous solution can be photocatalytic dehydrogenation formation of pinacol accompanied by the generation of hydrogen.In this article,we attempted to simultaneously convert acetone and isopropanol into pinacol by a light-driven dehydrogenation-hydrogenation coupling process using low-valent titanium reagents?TiCl₃?instead of noble-metal catalyst to achieve Mc Murry reaction without any reductive agent.This strategy not only utilizes electron?e-?and hole?h+?simultaneously to improve the photocatalytic efficiency,but also opens up a new green path to Mc Murry reaction.?2?We prepared a two-dimensional Ti O2 nanosheets instead of the traditional P25 TiO2 material,TiO2 as photocatalyst and TiCl₃ as co-catalyst to build a highly efficient light-driven McMurry reaction.The selectivity of isopropanol to acetone dehydrogenation-hydrogenation coupling to pinacol can reach 97.7%,and the conversion of the reaction solution is 29.1%,which provides the possibility for the industrial production of pinacol.?3?Sunlight is mainly composed of visible light and infrared light,only 5% of the UV light,and the TiO2 photocatalyst just response under UV light.In this paper,a series of C₃N₄/TiO2 heterojunction composite photocatalysts were synthesized by a simple one-step calcination.This kind of heterojunction composites can make the charge more efficiently separated in the photocatalytic application,simultaneously it can improve the photocatalytic activity.Most importantly it can respond in UV-Vis light,greatly improving the utilization of sunlight.?4?Aliphatic alcohol synthesis of acetal is an important industrial process,the industrial preparation of acetal method requires the use of corrosive acid catalyst and highly toxic solvents,the process is complex and low selectivity.In this paper,we use the C₃N₄/TiO2 heterojunction composites photocatalyst,the hole can generate acetal with the aliphatic alcohol,simultaneously the electron reduce the hydrogen ions into clean energy hydrogen,which can realize the efficient utilization of electrons and holes at the same time.And C₃N₄/TiO2 heterojunction complex photocatalyst can be widely used in a variety of first-class aliphatic alcohol acetalization reaction,the formation of acetal selectivity up to 98%,in addition,it can catalyze the conversion of secondary aliphatic alcohol to the corresponding ketone.The reaction of C₃N₄/TiO2 heterojunction composites catalyzed to synthesis the corresponding acetal in one step to achieve the green,high efficiency,simple operation and pollution-free photocatalytic organic synthesis process.