Sustainable development and environment protection is the important global theme in 21st century. It is well recognized by the world’s scientific, industrial and political communities that the atmospheric concentration of CO2 has been steadily increasing due to human activities and economic development, which accelerates the greenhouse effect. In 1997, the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) mandated a reduction of CO2 emission levels to below those of 1990. To reduce the CO2 emission and maintain a desired balance in atmosphere, new technologies have been developed. CO2 capture and storage is one of the approaches. It is also possible to convert CO2 to some reusable hydrocarbons or chemicals through physical, chemical and biological processes. The most important challenge is how to activate CO2 economically as it has high thermodynamic stability. Solar energy should be one of the best candidates because it is totally clean and abundant. Consequently, the highly efficient and selective photochemical reduction systems for CO2 are highly desired. In addition, alternative energy resources and technologies also play vital roles in the reduction of CO2 emission.