Tubular carbon nitrides with high nitrogen contents and tunable band structure and their superior ability for CO₂ capture and solvent sensing

Metal-free semiconducting carbon nitride materials with tunable band structure and rich functional groups afford new materials with ground-breaking features and potential applications in various areas. To obtain a mesoporous structure with high surface area and enhanced active sites utilizing templating is an effective strategy to further improve the performance of such functional materials, especially benefitting adsorption and sensing. Herein, hierarchical mesoporous graphitic carbon nitride showing tubular morphology and high nitrogen content were synthesized using economic halloysite nanoclay as the template and aminoguanidine as the CN precursor. Materials characterization and spectrum analysis revealed that the fabricated carbon nitride possessed mesoporous feature with tunable band structure and a C and N stoichiometry of C₃N_5.36. The optimized sample showed rich nitrogen content with a high specific surface area (214.2 m²/g), exhibiting superior adsorption performance for CO₂ (27.18 μmol m⁻² at 0 °C) and sensing over flammable aromatic and volatile aliphatic compounds. Besides, it was demonstrated as a promising sensor, exhibiting high stability and selectivity towards dichloromethane, a class 2 A carcinogen. The excellent performance of CO₂ capture and the sensing of toxic vapors is due to the tubular morphology, high surface area, and hydrophilic functionalities with more active sites for the adsorption on the surface of the materials.