Hierarchical Pd@PC-COFs as Efficient Catalysts for Phenol Hydrogenation

Abstract

One-step hydrogenation of phenol is a green approach to produce cyclohexanone, an important intermediate for the synthesis of nylon. The design and fabrication of high-performance catalysts still present a great challenge. Herein, a series of triazinyl covalent organic frameworks (PC-COFs) were prepared by adjusting the synthesis time using a solvothermal method, and then, Pd@PC-COF catalysts were fabricated by anchoring Pd. Controlling the synthesis time can lead to the fabrication of PC-COFs with high crystallinity, large specific surface area, abundant mesopores, and rich N element, increasing the Pd content with higher Pd(0) proportion and enhancing the mass transfer, thereby improving the catalytic performance of Pd@PC-COFs for phenol hydrogenation. The as-fabricated catalyst has good reusability during the reaction cycles of phenol hydrogenation. This work develops an efficient approach to fabricate high-performance Pd-based catalysts for phenol hydrogenation.

Pd-Decorated Hierarchically Porous Carbon Nanofibers for Enhanced Selective Hydrogenation of Phenol

“…The effects of reaction temperature and reaction time on the catalytic performance of Pd@CNFs-0.1–0.2 were further investigated. , It is seen from Figure c that with increasing reaction temperature, the conversion of phenol first increases significantly and then the increased trend slows down. However, the continuous rise in the reaction temperature will lead to the deep hydrogenation of cyclohexanone to cyclohexanol . Considering the phenol conversion and cyclohexanone selectivity comprehensively, it is determined that the optimal reaction temperature of 90 °C was used for next step optimization.…”

“…However, the continuous rise in the reaction temperature will lead to the deep hydrogenation of cyclohexanone to cyclohexanol. 74 Considering the phenol conversion and cyclohexanone selectivity comprehensively, it is determined that the optimal reaction temperature of 90 °C was used for next step optimization. With the prolongation of reaction time, the phenol conversion continues to rise (Figure 8d).…”

“…With the prolongation of reaction time, the phenol conversion continues to rise (Figure 8d). However, the prolongation of reaction time also brings about the further hydrogenation of cyclohexanone, 74 reducing the cyclohexanone selectivity. Comprehensively considering, the suitable reaction time is 60 min.…”

Insights into the Solvent Effect on the Synthesis of Pd@PC-COFs for Phenol Hydrogenation

“…According to the previous work, 38 PC-COFs were synthesized using a solvothermal method. Typically, 0.86 g of piperazine, 1.23 g of cyanuric chloride, and 2.76 g of K 2 CO 3 were introduced to a 250 mL three-necked bottle at room temperature, and then 100 mL of 1,4-dioxane was introduced.…”

“…The absorption peaks near 3400 and 2890 cm −1 belong to the stretching vibrations of N−H and C−H, respectively, suggesting the existence of triazine and piperazine units in the Pd@PC-COFs. 38 The peaks at about 1510 and 1434 cm −1 belong to the stretching vibrations of C−N and C�N, respectively. 38,47 The weak C−Cl stretching vibration at 850 cm −1 is due to the existence of cyanuric chloride in the Pd@PC-COFs.…”