Framework structure engineering of polymeric carbon nitrides and its recent applications

Polymeric carbon nitrides (CN) as star semiconductive materials have attracted increasing attention owing to its numerous superior features, such as facile synthesis, non-toxicity, earth-abundant, high physicochemical stability, and all of these endow its great potentials from photocatalysis to environmental remediation, sensing, biomedicine, and other emerging fields. The facile synthesis and polymeric characteristic of CN allow easy tailoring of their framework from elements, the structure of monomers, and tectonic units to control their properties and then to obtain superior performance in various applications. Although there have been reviews summarizing design and modification strategies of CN-based materials, most of them have focused only on surface engineering and nanostructure construction, lacking analysis from the point of view of the framework structure. This review systematically summarized the inspiring breakthroughs on rational design and fabrication of the CN framework from elements to monomers, and then to tectonic units via various strategies including elemental doping, defects engineering, tuning the crystalline degree, coordination engineering and molecular doping. Importantly, we summarized general rules between CN framework structure and their performance in various applications to better understand the current state-of-the-art status and plans for future research directions.