As a metal-free semiconductor, graphitic carbon nitride (g-C 3 N 4) has received extensive attention due to its high stability, nontoxicity, facile and low-cost synthesis, appropriate band gap in the visible spectral range and wide availability of resources. The dimensions of g-C 3 N 4 can influence the regime of the confinement of electrons, and consequently, g-C 3 N 4 with various dimensionalities shows different properties, making them available for many stimulating applications. Although there are some reviews focusing on the synthesis strategy and applications of g-C 3 N 4 , there is still a lack of comprehensive review that systemically summarises the synthesis and application of different dimensions of g-C 3 N 4 , which can provide an important theoretical and practical basis for the development of g-C 3 N 4 with different dimensionalities and maximises their potential in diverse applications. By reviewing the latest progress of g-C 3 N 4 studies, we aim to summarise the preparation of g-C 3 N 4 with different dimensionalities using various structural engineering strategies, discuss the fundamental bottlenecks of currently existing methods and their solution strategies, and explore their applications in energy and environmental applications. Furthermore, it also puts forward the views on the future research direction of these unique materials.

Three-dimensionally ordered macro/mesoporous Ce 0.6 Zr 0.3 Y 0.1 O 2 (3DOM CZY) supported high-dispersion Pt nanoparticles (x wt % Pt/3DOM CZY, x = 0.6, 1.1, and 1.7) were successfully synthesized via the cetyltrimethylammonium bromide/triblock copolymer P123 assisted gas bubbling reduction route. The 3DOM CZY and x wt % Pt/3DOM CZY samples exhibited a high surface area of 84−94 m 2 /g. Pt nanoparticles (NPs) with a size of 2.6−4.2 nm were uniformly dispersed on the surface of 3DOM CZY. The 1.1 wt % Pt/3DOM CZY sample showed excellent catalytic performance, giving a T 90% value at 598 °C at gas hourly space velocity (GHSV) of 30000 mL/(g h) and the highest turnover frequency (TOF Pt ) of 6.98 × 10 −3 mol/(mol Pt s) at 400 °C for methane combustion. The apparent activation energy (64 kJ/mol) over 1.1 wt % Pt/3DOM CZY was much lower than that (95 kJ/mol) over Bulk CZY. The effects of water vapor and SO 2 on the catalytic activity of 1.1 wt % Pt/3DOM CZY were also examined. It is concluded that the excellent catalytic activity of 1.1 wt % Pt/3DOM CZY was associated with its high oxygen adspecies concentration, good lowtemperature reducibility, and strong interaction between Pt NPs and CZY as well as large surface area and unique nanovoidwalled 3DOM structure.

Metal–organic frameworks (MOFs) are considered to be promising candidates for electrochemical water splitting. However, most MOFs are characterized by low electronic conductivity limiting their use as bulk materials for anodes and cathodes. Furthermore, the understanding of the critical parameters controlling the activity and stability of MOF electrocatalysts is still insufficient. Herein, a systematic analysis is presented of the key structural parameters controlling the oxygen evolution reaction (OER) performance and stability of a representative family of bimetallic NiFe‐MOFs, where the role of the metal cations on the accessible active sites and intrinsic activity can be investigated independently from the crystal structure. The models and in‐depth structural and morphological characterizations reveal a hierarchy of properties affecting the OER activity with accessible sites and intrinsic activity playing a major role in the charge transfer efficiency. Optimization of these properties and addition of a conductive support substrate leads to efficient MOF‐nanocomposite electrocatalysts achieving a low overpotential of 258 mV at a current density of 10 mA cm−2 with a small Tafel slope of 49 mV dec−1 and excellent stability for more than 32 h of continuous OER in alkaline medium.