Carbon Nitrides from Supramolecular Crystals: From Single Atoms to Heterojunctions and Advanced Photoelectrodes

Abstract

Carbon nitride materials (CN) have become within the last 15 years in one of the most studied photocataysts. While CN absorbs visible light, its low porosity and fast electron – hole recombination hinder its photoelectric performance and have motivated the research in the modification of its physical and chemical properties (such as energy band structure, porosity, or chemical composition) by different means. In this perspective we focus on the utilization of supramolecular crystals as CN precursors to tailor its properties. We elaborate on the features needed in a supramolecular crystal to serve as CN precursor, we delve on the influence of metal‐free crystals in the morphology and porosity of the resulting materials and then discuss the formation of single atoms and heterojunctions when employing a metal‐organic crystal. We finally discuss the performance of CN photoanodes derived from crystals and highlight the current standing challenges in the field.

Bio‐Inspired Supramolecular Self‐Assembled Carbon Nitride Nanostructures for Photocatalytic Water Splitting

“…[80] This section will discuss single-metal atom-based or sub-nanometer Figure 8. Schematic illustration of synthesis of a) B-doped, [62] b) S-doped CN, [63] and c) P-doped (heavy doping) CN [20,64] , via supramolecular selfassembly. a) Reproduced with permission.…”

“…[45a] Supramolecular assembly of CA and MA via hydrogen bonding was employed along with structure-directing property of ionic liquid to [26] c) MA-trithiocyanuric acid (M-T) complex, d) S-doped CN derived from M-T complex, [117] e) MA-Cu acetate complex, f) CuO-CN NRs. [90c] g) Schematic illustration of the synthesis for SS-CN via singlecrystal supramolecular precursor strategy [20] and SEM and optical images of h,i) single-crystal precursor (melaminium chloride hemihydrate crystals) and derived CN at j,k) 550 and l,m) 800 °C. [118] a,b) Reproduced with permission.…”

“…which are formed from routinely used precursors. [20] The formation mechanism of supramolecular graphitic carbon nitride involves the construction of stable intermediate supramolecularordered structural units via noncovalent interactions. These interactions are of electrostatic nature, van der Waals type, hydrophobic, intermolecular hydrogen bonding, and 𝜋-𝜋 stacking of nitrogen-rich single CN molecular precursors and/or a mixture of monomers.…”