Synthesis of Nitrogen‐Rich Mesoporous Carbon Nitride with Tunable Pores, Band Gaps and Nitrogen Content from a Single Aminoguanidine Precursor

Abstract

Highly ordered mesoporous carbon nitride (CN) with an extremely high nitrogen content and tunable pore diameters was synthesized by using a new precursor with a high nitrogen content, aminoguanidine hydrochloride and mesoporous silica SBA-15 with different pore diameters as hard templates. Surprisingly, the N/C ratio of the prepared mesoporous CN (MCN-4: 1.80) was considerably higher than that of the theoretically predicted C(3)N(4) nanostructures (1.33). This is mainly due to the fact that the CN precursor easily undergoes polymerization at high temperature and affords a highly stable polymer composed of a diamino-s-tetrazine moiety with a six-membered aromatic ring containing six nitrogen atoms that are linked trigonally with the nitrogen atoms. The obtained materials were thoroughly characterized by means of XRD, nitrogen adsorption, high resolution TEM, electron energy loss spectra, high resolution SEM, X-ray photoelectron spectroscopy, FTIR, and C, N, O, and S analysis. The results show that the MCN-4 materials possess a well-ordered mesoporous structure similar to SBA-15 with a high specific surface area and tunable band gap in the range of 2.25-2.49 eV. Interestingly, the pore diameter of the materials can be finely tuned from 3.1-5.8 nm by increasing the pore diameter of the hard-template SBA-15. The reaction temperature plays a critical role for the formation of MCN, and we found that 400 °C is the best condition to obtain MCN-4 with a high nitrogen content. We have further investigated the catalytic application of the MCN-4 materials towards Friedel-Crafts hexanoylation of benzene and compared the results with the mesoporous CN with less nitrogen content (MCN-1) and nonporous CN. Among the materials studied, MCN-4 showed the highest activity, affording a high yield of hexanophenone within a few hours, which is mainly due to the presence of free amine groups on the wall structure of MCN-4.

Superior carbon-based CO2 adsorbents prepared from poplar anthers

“…This is further confirmed by the XPS spectroscopy measurements that the signal ascribed to N 1 s was observed at the binding energy of 400 eV in the spectra of all the samples (Fig. S7) [47,48]. Table 1 shows that the nitrogen contents decreased when the KOH amount or activation temperatures was increased.…”

Design and synthesis of W-containing mesoporous material with excellent catalytic activity for the oxidation of 4,6-DMDBT in fuels

“…3A) reflected the feature of mesoporous structure. However, the diffraction peaks were weak, which indicated that disordered mesoporous structure were formed during the removal of template [56,57]. In Fig.…”

Synthesis of nanoporous carbon nitride using calcium carbonate as templates with enhanced visible-light photocatalytic activity

“…The fabrication of porous g-C 3 N 4 with high surface area and tunable pore diameter is particular interest because a larger surface area of photocatalyst can be favorable for the photoactivity by providing more contact chances between the photocatalysts and substances. Template method is commonly used to 6 synthesize the porous structure and improve the surface area of g-C 3 N 4 [36,37]. Porous silica or porous anodic aluminium oxides are used as hard templates during condensing procursors to carbon nitride, which would be subsequently removed by dissolving in some hazardous reagents such as ammonium bifluoride (NH 4 HF 2 ) and hydrogen fluoride (HF) [38,39].…”