Preparation of mesoporous graphitic carbon nitride using hexamethylenetetramine as a new precursor and catalytic application in the transesterification of β-keto esters
Hexamethylenetetramine has been utilized as a low-cost and widely available precursor for the synthesis of mesoporous graphitic carbon nitride (CN-H-SBA15) through a nanocasting route. The synthesized CN-H-SBA15 material possesses a high surface area (788 m2 g−1), a large pore volume (0.68 cm3 g−1), and rich N content (N/C = 0.277). The characterization results of transmission electron microscopy and small-angle X-ray scattering illustrated that CN-H-SBA15 successfully replicated the ordered mesostructures of SBA-15. As a heterogeneous base catalyst, CN-H-SBA15 exhibits efficient and stable activity in the transesterification reactions of β-keto esters, affording a maximum conversion of n-butanol of 70% at 110 °C. The catalytically active sites are proposed as the tertiary amine species of CN-H-SBA15, as revealed by Fourier transform infrared and X-ray photoelectron spectroscopy. Furthermore, the catalytic performance in the transesterification reaction was compared with those of other previously reported catalysts; the results show that CN-H-SBA15 can be served as a promising heterogeneous catalyst towards the transesterification of β-keto esters.