Abstract
The development of environmentally benign catalysts for highly regioselective hydroxylation of phenol remains an unsolved challenge in both industry and academia because the electrophilic substitution of phenol simultaneously occurs on bothortho- andpara-positions. Herein, we report a designed atomically dispersed iron-based heterogeneous catalyst, in which the iron species is coordinated by a functionalized ionic liquid monolayer on carbon nanotubes. The catalyst exhibits an unprecedented level of regioselectivity (>99%) towards the hydroxylation of phenol and displays a much better activity (TOF towards catechol productivity, 1.79 s−1) compared to the homogeneous free ion system (TOF towards catechol productivity, 0.44 s−1). Both experimental and theoretical investigations confirm that the catalytic oxidation with hydroperoxide undergoes a non-radical addition process and substitutes only theortho-positions of phenol. This finding provides not only a quite active and selective catalyst for industrially very important reactions, but also a promising methodology of designing biomimetic iron-based heterogeneous catalysts at the atomic level.
| Original language | English |
|---|---|
| Pages (from-to) | 6025-6032 |
| Number of pages | 8 |
| Journal | Green Chemistry |
| Volume | 22 |
| Issue number | 18 |
| DOIs | |
| State | Published - Sep 21 2020 |
Funding
The authors acknowledge the funding support from the Max Planck Society. Zhen-An Qiao was supported by the National Natural Science Foundation of China (21671073 and 21621001), the “111” Project of the Ministry of Education of China (B17020), and the Program for JLU Science and Technology Innovative Research Team. Prof. Dr Shengfa Ye is thanked for the fruitful discussion. The authors thank Prof. Dr Robert Schlögl for the useful suggestions. Ding thanks Prof. Dr Dang Sheng Su for his support in the manuscript preparation and guidance in his scientific career. Open Access funding was provided by the Max Planck Society.