H3PW12O40/mpg-C3N4 as an efficient and reusable bifunctional catalyst in one-pot oxidation-Knoevenagel condensation tandem reaction

作者：Wang, Hefang; Wang, Cunyue; Yang, Yongfang^*; Zhao, Meng; Wang, Yanji^*

来源：Catalysis Science & Technology, 2017, 7(2): 405-417.

DOI：10.1039/c6cy01669c

• MESOPOROUS CARBON NITRIDE
• METAL-ORGANIC FRAMEWORK
• LAYERED DOUBLE HYDROXIDES
• SOLID BASE CATALYST
• PHOSPHOTUNGSTIC ACID
• SELECTIVE OXIDATION
• HYDROGEN-PEROXIDE
• CASCADE REACTIONS
• BENZYL ALCOHOL
• OXIDATION/KNOEVENAGEL CONDENSATION

A single-site bifunctional catalyst for the oxidation-Knoevenagel condensation tandem reaction was prepared by the immobilization of phosphotungstic acid (HPW) on mesoporous graphitic carbon nitride (mpg-C3N4) via electrostatic interaction (HPW/mpg-C3N4). The results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state P-31 nuclear magnetic resonance (solid-state P-31 NMR), zeta potentials, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated that HPW was successfully immobilized on the protonated mpg-C3N4 by electrostatic interaction. The acid amounts of the catalysts were determined by NH3 temperature programmed desorption (NH3-TPD). The textural properties and morphology of HPW/mpg-C3N4 were characterized by N-2 adsorption-desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 30% HPW/mpg-C3N4 shows the best catalytic performance in the tandem reaction with 98.4% benzyl alcohol conversion and 96.2% selectivity to benzylidene malononitrile. The excellent catalytic performance of 30% HPW/C3N4 in the tandem reaction is due to the good catalytic performance of HPW in the oxidation and Knoevenagel condensation, respectively. Furthermore, protonated mpg-C3N4 not only acts as a support to facilitate good dispersion of HPW but also promotes the Knoevenagel condensation reaction effectively. Moreover, the HPW/mpg-C3N4 catalyst could be recycled easily without significant loss of catalytic activity.

• 出版日期2017-1-21
• 单位河北工业大学