Selective sensing performance of mesoporous carbon nitride with a highly ordered porous structure prepared from 3-amino-1,2,4-triazine

Abstract

We demonstrate the preparation of highly ordered and graphitic mesoporous carbon nitride with an ordered porous structure and a high nitrogen content (MCN-ATN) by a nano-hard-templating approach through a simple polymerization of 3-amino-1,2,4-triazine (ATN) inside the pore channels of a mesoporous silica template with an Ia3d symmetry and a 3D porous structure. Powder X-ray diffraction and high resolution transmission electron microscopy analysis show that the prepared materials exhibit well-ordered mesopores with a 3D porous network. Nitrogen adsorption measurements also confirm that the samples possess excellent physical parameters including high surface areas (472–635 m² g⁻¹), large pore volumes (0.71–0.99 cm³ g⁻¹) and tunable pore diameters (5.5–6.0 nm). One of the most important features of this work is that the cyclic aromatic precursor helps to preserve the nitrogen in the carbon matrix of the final product even after the carbonization process. The C/N ratio of the samples is ca. 0.92 which is much lower than that obtained for the samples prepared using ethylene diamine and carbon tetrachloride through a nano-hard templating process. X-ray photoelectron spectroscopy results reveal that MCN-ATN is mainly composed of sp² hybridized carbon atoms bonded with nitrogen atoms, associated with the triazine moieties from the ATN molecules. Temperature programmed desorption of CO₂ over MCN-ATN demonstrates that the sample is basic which originates from the amine groups on the surface of the CN wall structure. Finally, the samples are mounted on the quartz crystal microbalance (QCM) and used for sensing both acidic and basic organic vapors. Among the samples studied, MCN-ATN with the largest pore diameter showed a highly selective sensing performance for acidic molecules, especially the formic acid thanks to the presence of weak basic sites on the CN walls.