Supporting Information

Promoting the aerobic Baeyer-Villiger oxidation of ketones over

carboxylic multi-walled carbon nanotubes

Shao-Yun Chena, Xian-Tai Zhoub*, Jie-Xiang Wanga, Rong-Chang Luoa, Qing-Jin Luoc, Liang-

Jun Yuc, Hong-Bing Jia*

a Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, PR China

b Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai, 519082, PR China

c Huizhou Yussen Chemical Co. Ltd, Huizhou, 516081, PR China

E-mail address: jihb@mail.sysu.edu.cn (H. Ji), zhouxtai@mail.sysu.edu.cn (X. Zhou)

1. TEM and XPS characterization of MWCNTs and c-MWCNTs

The microstructures of MWCNTs and c-MWCNTs were shown in Figure S1, and the XPS

was used to identify the chemical composition of the MWCNTs and c-MWCNTs surface to get

the accurate elements distribution (Figure S2, Table S1). Figure S2 (a1) showed wide-scan

spectra of MWCNTs, Figure S2 (a2) was the C1s spectrum of MWCNTs curve-fitted with one

peak components and the binding energies (BEs) at 284.8 eV, attributing to sp2 of C–C bond.

Figure S2 (a3) was O1s spectrum of contaminative oxygen during the testing which curve-fitted

with two peak components and the binding energies (BEs) at 532.1 and 533.7 eV. The XPS C1s

spectrum of c-MWCNTs originated from the C–C and carboxyl group (O=C–O–H) species being

curve-fitted with two peak components with BEs at about 284.8 and 290.8 eV (Figure S2 (b2)),

and O1s spectrum of c-MWCNTs came from the carboxyl group which curve-fitted with two

peak components and the BEs at 532.5 and 533.5 eV (Figure S2 (b3)).

Figure S1 (a) Low and high-magnification TEM images of MWCNTs and c-MWCNTs.

Figure S2 (a1) The XPS spectrum of MWCNTs, (a2), (a3) the C1s and O1s core-level spectra of

fresh MWCNTs, respectively. (b1) The XPS spectrum of fresh c-MWCNTs, (b2), (b3) the C1s

and O1s core-level spectra of c-MWCNTs, respectively.

Table S1 XPS data for fresh MWCNTs and fresh c-MWCNTs

Surface atom ratio

C/% O/% C/O

Fresh MWCNTs 97.68 2.32 42.10

Fresh c-MWCNTs 97.09 2.91 33.36

2. Reaction profiles of cyclohexanone B-V oxidation with MWCNTs and c-MWCNTs

Figure S3 showed the profiles of cyclohexanone aerobic oxidation promoted by MWCNTs and

c-MWCNTs, respectively. The yield of -caprolactone increased rapidly within 4 h period.

While, no significant increase was observed when the reaction time was prolonged. Therefore,

the optimized reaction time was 4 h.

Figure S3 Catalytic activity of MWCNTs and c-MWCNTs in aerobic liquid phase oxidation of

cyclohexanone. Conditions: 10 mg catalyst, 2 mmol cyclohexanone, 4 mmol benzaldehyde, 10

mL DCE, O2 balloon, 50 °C.

3. The stability of c-MWCNTs confirmed by FTIR, XRD, TEM and Raman

Cycling tests indicated that c-MWCNTs were stable during the oxidation process in Figure

1. Hence, FTIR, XRD, TEM and Raman were employed to further clarify the stability of c-

MWCNTs. Figure S4 (a) showed the FTIR results of the fresh and recover c-MWCNTs. Both of

the samples showed the same absorption bands at 3430, 2922, 1635, 1383 and 1058 cm-1. The

strong absorption band at 1635 cm-1 is assigned to the carbonyl vibration band corresponding to

the carboxylic acid (–COOH) stretching and the band at 1058 cm -1 is correlated with the C–O

vibration. The intense absorption band at 3430 cm-1 corresponds to the –OH stretching vibration

of carboxylic acid. The band at 2922 cm-1 belongs to the C–H stretching and 1383 cm-1 belongs

to the hydrogen bond (H bonds).

The XRD patterns acquired for fresh and recover c-MWCNTs were shown in Figure S4 (b).

The diffraction peaks at 26.3。and 42.6◦ for c-MWCNTs are attributed to (002) and (100) planes

of hexagonal graphite and appearance of these peaks with high intensity suggested that the

original structure of c-MWCNTs did not change. The typical TEM images of fresh and recover

(5 runs) c-MWCNTs catalysts were shown that the morphologies obviously remained unchanged

before and after using (Figure S4 (c-d)). The Raman spectra of fresh and recover c-MWCNTs

(Figure 4(a) and (c)) revealed the existence of characteristic D band and G-band around 1329 cm-

1 and 1578 cm-1, respectively. In addition, the D*-band was displayed for all the samples around

2656 cm-1 and the D2-band, a shoulder of the G-band was observed around 1612 cm-1. The detail

information of all bands is summarized in Table S2. These bands almost unchanged after five

cycles of catalytic reaction, the intensity ratio (ID/IG) of the D and G bands are both 1.05. In a

word, the stability of c-MWCNTs is good enough to work continuously in the present reaction

conditions.

Figure S4 The (a) FTIR spectra and (b) the XRD patterns of fresh and recover c-MWCNTs. (c)

and (d) are TEM images of fresh and recover c-MWCNTs.

Table S2 Raman bands displayed for fresh, reactive and recover c-MWCNTs

Position of band (cm−1)

ID/IG

D-band G-band D2-band D*-band

fresh 1329 1579 1612 2656 1.05

reactive 1332 1584 1617 2666 1.14

recover 1329 1579 1612 2656 1.05

4. EPR evidence for the initiation reaction occurred from the dehydrogenation of

benzaldehyde

EPR evidence for the initiation reaction occurred from the dehydrogenation of

benzaldehyde to obtain C6H5CO• was shown in Figure S5. Figure S5 (a) revealed a six-line

spectrum consisting of a triplet of doublets (, aN=1.35 mT, aH=0.17 mT, g=2.0033) in the

presence of benzaldehyde and PBN. When O2 was added into the benzaldehyde system (see

Figure S5 (b)), a new radical signal was obviously observed with a set of triplet peak at about

g=2.0035 (♣, aN=0.81 mT), attributed to acylperoxy radical (C6H5COOO•) adduct, which was

consistent with previous studies. Thus, it can be concluded that the mechanism of c-MWCNTs-

catalyzed cyclohexanone oxidation was reasonable.

Figure S5 In situ EPR spectra of (a) benzaldehyde+PBN and (b) benzaldehyde+PBN+O2.

Reaction conditions: (a) 2 ml 1,2-dichloroethane solution containing 0.3 mmol benzaldehyde and

0.1 mmol PBN, 50 oC. (b) 2 ml O2-saturated dichloroethane solution containing 0.3 mmol

benzaldehyde and 0.1 mmol PBN, 50 oC.

5. Raman spectra for MWCNT

As shown in the Figure S6(b), there was shift in the spectral position of the G-band upon

active radical adsorption. The most intense peak at G-band shifted from 1570 cm-1 to 1575 cm-1.

The shift in the G-band was consistent with C-C bond length expansion expected upon electron

injection and as observed in alkali metal doping of nanotube and graphite systems. The intensity

ratio (ID/IG) of the D and G bands remained unchange (1.03). But as to c-MWCNTs, the intensity

ratio (ID/IG) of the D and G bands increased from 1.05 to 1.14 (Figure 4). Compared with

MWCNTs, c-MWCNTs is more easily to undergo electron transport with free radicals during the

reaction.

Figure S6 Raman scattering spectra for fresh, reactive and recover c-MWCNTs.