Abstract
Utilizing CO(2) as a sustainable carbon source to form valuable products requires activating it by active sites on catalyst surfaces. These active sites are usually in or below the nanometer scale. Some metals and metal oxides can catalyze the CO(2) transformation reactions. On metal oxide-based catalysts, CO(2) transformations are promoted significantly in the presence of surface oxygen vacancies or surface defect sites. Electrons transferable to the neutral CO(2) molecule can be enriched on oxygen vacancies, which can also act as CO(2) adsorption sites. CO(2) activation is also possible without necessarily transferring electrons by tailoring catalytic sites that promote interactions at an appropriate energy level alignment of the catalyst and CO(2) molecule. This review discusses CO(2) activation on various catalysts, particularly the impacts of various structural factors, such as oxygen vacancies, on CO(2) activation.