(1)Advanced Oxidation Process(AOPs) AOPs such as photocatalysis and Fenton reaction possess unique edges on treating wastewater with refractory organic pollutants. (2) Photoreduction of CO2 Facing the greater greenhouse effect, the breakthrough on photoreduction of CO2 is urgently needed. (3) Photocatalytic water splitting. H2 production from photocatalytic water splitting is a promising solution for energy crisis.