CO2 is regarded as the primary greenhouse gas. Its conversion into reusable fuels over photocatalysts attracts much attention
and many papers are published in recent years. The photocatalytic activity is an important term in evaluating the photocatalyst performance,
which is not only determined by types of photocatalysts, but also closely related with the other factors, such as the sizes, morphologies,
exposed crystal facets, and the surface area etc. These latter factors can be classified into microstructure. In this review, efforts on
improving the photocatalytic activity of CO2 reduction via microstructure modulations are presented, and are discussed from six aspects,
namely, crystal facets, nanostructure, mesoporous structure, crystal phase, oxygen vacancy, and surface functionalization.