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Nanocarbon-based TEMPO as stableheterogeneous catalysts for partial oxidation of alcohols

Yongbin Sun, Changyan Cao,* Fang Wei, Peipei Huang, ShuliangYang and Weiguo Song*

CAS Key Laboratory of Molecular Nanostructures and Nanotechnology, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

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1. Experimental section

1.1 Materials

Toluene, hydrogen peroxide (30 wt%), 1,6-hexanediamine (HDA), ethanol, dichloromethane, sodium bicarbonate, potassium bromide, and sodium hypochlorite (10% active chlorine) were purchased from Sinopharm Chemical Reagent Beijing Co., Ltd. C60 was purchased from Suzhou Dade Carbon Nanotechnology Co., Ltd. Tetrabutylammonium hydroxide (40 wt% solution in water) was purchased from Beijing InnoChem Science & Technology Co., Ltd. 4-Amino-2,2,6,6-tetramethylpiperidinooxy (4-amino-TEMPO) was purchased from Adama's Reagent Co., Ltd. All the reagents used for oxidation reactions were purchased from Alfa Aesar. All the reagents were used without further purification.

1.2 Sample preparation

(1) Preparation of C60-TEMPO derivative. C60 108 mg (0.15 mmol) was dissolved in 60 mL toluene, this purple solution was labeled as A. 4-Amino-TEMPO642 mg (3.75 mmol, 25 equiv.) was dissolved in 4 mL water, then 0.85 mL H2O2 (30 wt%, 7.5 mmol, 50 equiv.) was added. This red solution was mixed with solution A, and 5 drops of tetrabutylammonium hydroxide (40 wt%) was addedas a phase transfer catalyst. After stirred for 60 min at 60 oC, the upper light red toluene solution was removed, and the lower aqueous mixture was addedwith the mixture of ethanol and ether (volume ratio 1:3). The solid was collected by centrifugation and washed two times with ether. The obtained product was dried at 60 oC for 12 h.

During the process of C60-TEMPO preparation, the toluene became nearly colorless after 60 min, indicated all C60participated in amination reactions. Based on themass ratioofcarbon and nitrogen, the average number of TEMPO attached onto one C60molecule was determined to be about 5. When the reaction time was decreased to 30 min, this number was only 3, but a longer reaction time (90 min)did not increase this number. It indicated C60 was not easy to react with more molecules due to steric hindrance after 60 min. Thus, in the process of preparing C60-TEMPO, the reaction time is 60 min, and for C60-TEMPO-HDA, the reaction time is 30 min.

(2) Preparation of C60-HDA derivative.C60 108 mg (0.15 mmol) was dissolved in 60 mL toluene, this purple solution was labeled as A. 1,6-hexanediamine 174 mg (1.5 mmol, 10 equiv.) was dissolved in 4 mL water, then 0.51 mL H2O2 (30 wt%, 4.5 mmol, 30 equiv.) was added. This solution was mixed with solution A, and 5 drops of tetrabutylammonium hydroxide (40 wt%) was addedas a phase transfer catalyst. After stirred for 60 min at 60 oC, the upper toluene was removed, and 20 mL ethanol was added into the residual mixture. The solid was collected by filtration and washed with ethanol for 3 times. The product was dried at 60 oC for 12 h.

2. Supporting Figures and Tables

Fig.S1(a)1H NMR and (b) 13C NMR spectrum of C60-TEMPO derivative

Fig.S2TEM image of C60-HDA derivative

Fig.S3 N2 sorption isotherms of C60-HDA and C60-TEMPO-HDA

Fig. S4XPS spectrum of C60-TEMPO-HDA

Fig.S5TEM image of C60-TEMPO-HDA after six times reused

Fig.S6Solid state ESR spectrum of C60-TEMPO-HDA after six times reused

Table S1 Element analysis of different catalysts