Advances in the solar-energy driven conversion of methanol to value-added chemicals

With the rapid increase of methanol reservoirs, catalytic transformation of methanol into value-added chemicals is receiving ever increasing attention. Conventional thermocatalysis enables the production of an array of chemicals from methanol conversion, but high temperatures and high pressures with intensive energy input are generally required. Moreover, the harsh conditions of thermocatalysis preferentially accelerate the cleavage of C-O and O-H bonds instead of C-H bonds in methanol, mainly producing hydrocarbons, olefins or dimethyl ether. The direct C-C coupling products such as ethylene glycol via C-H activation cannot be readily obtained. Because photocatalysis utilizes solar energy to drive the reaction, the photocatalytic conversion of methanol not only can be performed at room temperatures and atmospheric pressures, but can also provide very different product distribution from thermocatalysis due to its radical mechanism. Thus, much effort has been devoted to the photocatalytic transformation of methanol in the past decade. Herein, we highlighted the recent advances in the development of photo-catalysts for the synthesis of ethylene glycol, ethanol, formaldehyde, 1,1-dimethoxy-methane and methyl formate. Emphasis is put on the reaction mechanism of typical catalysts and the key factors that affect the catalytic performances. The challenges and opportunities of methanol conversion are also presented.