With the rapid development of science and technology, environmental pollution and energy shortage become more and more prominent. To solve these problems, photocatalytic technology is regarded as one of the most efficient methods, allowing for both pollutant degradation and energy conversion. Compared with traditional group II-VI, III-V quantum dots (QDs), carbon dots (CDs), as a newly emerging kind of fluorescent carbon-based material, possess many excellent properties, such as high aqueous solubility, low cost, low toxicity, abundant surface functional groups and good biocompatibility. In particular, the unique up-converted photoluminescence (PL) behavior and photo-induced electron transfer ability of CDs provide the new route to achieve efficient metal-free photocatalysts. This article reviews recent progress on CDs utilized for photocatalysis from different perspectives, including the following three parts: classification and synthesis, mechanism of CDs-derived photocatalysts as well as the applications for environmental issues (up-converted PL process) and energy conversion (photo-induced electron transfer process). (C) 2018 Elsevier Ltd. All rights reserved.