Facile Soft-Templated Synthesis of High-Surface Area and Highly Porous Carbon Nitrides

Mesoporous carbon nitride is synthesized in a one-pot approach using different nonionic surfactants (Pluronic F-127, Pluronic P-123, and Triton X-100) and a melamine cyanurate hydrogen-bonded complex using just water as the solvent. We obtain three-dimensional assembled nanostructures from low-dimensional carbon nitride sheets by taking advantage of supramolecular assembly of melamine and cyanuric acid, moderate interactions between the surfactant and precursors, structure directing effects of the surfactants, and the good thermal stability of the melamine cyanurate sheets formed around the micelles. Different morphologies, including sheetlike, hollow spherical, and tubular or highly porous networks, result depending upon the synthesis approach and the surfactant/precursor ratio. Pseudoternary phase diagrams map the composition of the starting solution to the resultant carbon nitride morphology. Increasing the amount of surfactant leads to a higher carbon residue (C/N ∼ 1) and large BET surface areas (≤300 m²/g). Further tuning of the synthesis parameters as well as addition of HCl produces uniformly porous nanostructures with a high porosity (up to 0.8 cm³/g), a high surface area (>200 m²/g), and yet a stoichiometric C/N ratio (∼0.75). The synthesized high-surface area carbon nitrides show improved light absorption and enhanced photocatalytic activity in a rhodamine B dye degradation reaction under visible light irradiation compared to those of bulk melamine-derived carbon nitride.