The persistent increase of CO 2 levels in the atmosphere, already exceeding 400 ppm, urges the exploration of CO 2 emission reduction and recycling technologies. Ideally, photocatalytic conversion of CO 2 into valuable hydrocarbons realizes solar-to-chemical energy conversion, which is a desirable "kill two birds with one stone" strategy; namely, CO 2 photoreduction can simultaneously tackle energy shortage and keep global carbon balance.Graphitic carbon nitride (g-C 3 N 4 ) working on CO 2 reduction reaction deserves a highlight not only for the metal-free feature that endows it with low cost, tunable electronic structure, and easy fabrication properties but also because of its strong reduction ability. The present review concisely summarizes the latest advances of g-C 3 N 4 -based photocatalysts toward CO 2 reduction. It starts with the discussion of thermodynamics and dynamics aspects of the CO 2 reduction process. Then the modification strategies to promote g-C 3 N 4 -based photocatalysts in CO 2 photoreduction have been discussed in detail, including surface functionalization, molecule structure engineering, crystallization, morphology engineering, loading cocatalyst, and constructing heterojunction.Meanwhile, the intrinsic factors affecting CO 2 reduction activity and selectivity are analyzed and summarized. In the end, the challenges and prospects for the future development of highly g-C 3 N 4 -based photocatalysts in CO 2 reduction are also presented. K E Y W O R D SCO 2 reduction, g-C 3 N 4 , photocatalysis, solar-to-fuel conversion Carbon Energy.

Generally, bulk graphic carbon nitride (g-C 3 N 4) suffers from fast photogenerated charge carrier combination, inferior light absorption and insufficient active sites. Herein, we developed a defect engineering approach which can simultaneously realize O dopant and N defects in the g-C 3 N 4 framework via an acid-assisted thermal treatment route. The modified g-C 3 N 4 demonstrated greatly enhanced photocatalytic H 2 activity with a H 2 evolution rate of 2.20 mmol • g À 1 • h À 1 , which is more than three times higher than that of bulk g-C 3 N 4. The mechanism of the enhanced activity was investigated and proposed that the introduction of O dopants and N defects in the g-C 3 N 4 could optimize the electron structure, up-shift the conduction band, increase the surface area, and thus achieve more efficient separation of photogenerated carriers, stronger reduction ability and abundant active sites for photocatalytic H 2 evolution. Thus, defect engineering has been demonstrated to be a prospective strategy to modify the performance of g-C 3 N 4 for future photocatalytic energy generation.

Graphitic carbon nitride (g‐C3N4) is a prominent polymer photocatalyst, yet it suffers from severe charge carrier recombination in photocatalysis. Herein, carbon nanotubes (CNTs) are in situ grown onto g‐C3N4 nanosheets via a chemical vapor deposition (CVD) process, catalyzed by Au nanoparticles (NPs) pre‐deposited on g‐C3N4 surface via deposition‐precipitation. Systematic characterizations, in particular femtosecond transient absorption spectroscopy (fs‐TAS) and time‐resolved photoluminescence (TR‐PL), prove that CNTs can efficiently extract the localized electrons in the tri‐s‐triazine units of g‐C3N4, thereby enhancing charge carrier diffusion and separation. As a result, CNT/Au/g‐C3N4 nanocomposites display a H2 evolution rate of 0.95 mmol g−1 h−1, which is about three times higher than that of Au/g‐C3N4. This work may pave a path to explore the full potential of CNTs to modify g‐C3N4 or other photocatalysts in solar‐to‐chemical energy conversion.

COF-LZU1 with cubic hollow structure was fabricated through a hard template approach by using water solvable NaCl as template. The precisely prepared COF-LZU1 hollow cube displays enhanced H2 evolution rate...