PAPER www.rsc.org/materials | Journal of Materials Chemistry

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Zeolite confined nanostructured dinuclear ruthenium clusters: preparation,characterization and catalytic properties in the aerobic oxidation of alcoholsunder mild conditions

Mehmet Zahmakıran and Saim €Ozkar*

Received 1st June 2009, Accepted 21st July 2009

First published as an Advance Article on the web 11th August 2009

DOI: 10.1039/b910766e

Zeolite confined nanostructured dinuclear ruthenium clusters as a novel material were prepared by

a simple three step procedure: (i) the ion-exchange of Ru3+ ions with the extra-framework Na+ ions in

zeolite-Y, (ii) reduction of the Ru3+ ions within the cavities of zeolite with borohydride ions in aqueous

solution all at room temperature, (iii) drying the isolated samples under aerobic conditions at

100� 1.0 �C. The composition, morphology and structure of zeolite confined nanostructured dinuclear

ruthenium clusters, as well as the integrity and crystallinity of the host material, were investigated

by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, Raman, FTIR, Ru K-edge

XANES, EXAFS spectroscopies, and N2-adsorption/desorption technique. The results of these multi-

pronged analyses reveal the formation of nanostructured dinuclear ruthenium clusters within the

cavities of zeolite-Y, in which each ruthenium center exists in the oxidation state of 3+ and is

surrounded by one oxygen of the zeolite framework and three hydroxyl ligands, without causing

alteration of the framework lattice, mesopore formation, or loss of crystallinity of the host material.

The catalytic use of zeolite confined nanostructured dinuclear ruthenium(III) clusters was tested in the

aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl

compounds and found to provide exceptional catalytic activity and selectivity under mild conditions

(80 �C and 1 atm O2 or air).

Introduction

Fabrication of transition metal and metal oxide nanoparticles

with controllable size and size distribution is of great importance

because of their potential applications in many fields, including

catalysis.1 However, in their catalytic application one of the most

important problems is the aggregation of nanoparticles into

clumps and ultimately to the bulk metal, despite using good

stabilizers,2 which leads to a decrease in catalytic activity and

lifetime. The utilization of microporous and mesoporous mate-

rials as hosts for the preparation of metal and metal oxide

nanoparticles appears to be an efficient way of preventing

aggregation.3 Zeolite-Y, a faujasite (FAU) type zeolite, is

considered to be a suitable host providing highly ordered large

cavities with a diameter of 1.3 nm,4 and can be used for the

assembly of metal and metal oxide nanoclusters as the pore size

restriction could limit the growth of particles.5 Moreover, metal

and metal oxide nanoparticle catalysts encapsulated within the

cavities of zeolite or between the zeolite-supported layers (i.e.,

zeolite films, powders or membranes supported on the surface of

solid materials)6 may provide the control of kinetics for the

catalytic reactions.

Herein, we report the preparation of zeolite confined nano-

structured dinuclear ruthenium clusters as a novel material,

hereafter referred to as ZC–Ru, by using an easy and efficient

Department of Chemistry, Middle East Technical University, 06531Ankara, Turkey. E-mail: sozkar@metu.edu.tr; Fax: +903122103200;Tel: +903122103212

7112 | J. Mater. Chem., 2009, 19, 7112–7118

three step procedure. Using a combination of advanced analyt-

ical methods including ICP-OES, XRD, XPS, SEM, TEM,

HRTEM, TEM/EDX, Raman, FTIR, Ru K-edge XANES and

EXAFS spectroscopies and N2-adsorption technique we show

the formation of nanostructured dinuclear ruthenium clusters

within the cavities of zeolite-Y. The work reported here also

includes the catalytic application of ZC–Ru in the aerobic

oxidation of alcohols to carbonyl compounds which is one of the

most important and challenging transformations in the synthesis

of fine chemicals and intermediates7 and traditionally has been

carried out with stoichiometric amounts of oxidant.8 Unfortu-

nately, most of these oxidants are toxic, hazardous or are

required in large excess and some of these processes generate

equal amounts of metal waste.9 Therefore, the development of

green, effective, selective, and reusable catalysts for the oxidation

of alcohols to carbonyl compounds by only molecular O2 as

oxidant is of great importance from both economic and

environmental points of view.

Experimental

Materials

Ruthenium(III) chloride (RuCl3$xH2O), sodium borohydride

(NaBH4, 98%), and toluene were purchased from Aldrich.

Ruthenium(III) chloride was recrystallized from water and the

water content of RuCl3$xH2O was determined by TGA and

found to be x ¼ 3. All alcohols and carbonyl compounds were

reagent grade and purchased from Sigma and were used without

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further purification. Sodium zeolite-Y (Na56Y) (Si/Al ¼ 2.5) was

purchased from Zeolyst Inc. Deionized water was distilled by

a water purification system (Milli-Q system). The ruthenium

content of zeolite confined nanostructured dinuclear ruthenium

clusters was determined by inductively coupled plasma optical

emission spectroscopy, ICP-OES (Leeman Labs.). All glassware

and Teflon coated magnetic stir bars were cleaned with acetone,

followed by copious rinsing with distilled water before drying in

an oven at 150 �C.

Preparation of zeolite confined nanostructured dinuclear

ruthenium clusters

Zeolite-Y was slurried with 0.1 M NaCl to remove sodium defect

sites, washed until free of chloride and calcined in dry oxygen at

500 �C for 12 h. Ruthenium cations were introduced into the

zeolite-Y by ion exchange4 of 1.0 g zeolite-Y in 100 mL aqueous

solution of 78 mg RuCl3$3H2O for 72 h at room temperature. It

was observed that after 72 h the opaque supernatant solution

became colorless, indicating the completion of ion exchange. The

sample was then filtered by suction filtration (under 0.1 Torr

vacuum) using Whatman-1 (90 mm) filter paper, washed three

times with 20 mL of deionized water and the remnant was dried

at ambient temperature. The ruthenium content of the Ru3+-

exchanged zeolite-Y sample was found to be 2.4 wt % by

ICP-OES analysis. Then, 0.8 g Ru3+-exchanged zeolite-Y was

added into 100 mL of 0.1 mol NaBH4 solution at room

temperature. When the hydrogen generation from the reaction

solution finished (less than 5 minutes), the solid powders were

isolated again by suction filtration, washed three times with

20 mL of deionized water to remove metaborate and chloride

anions and dried in an oven at 100 � 1.0 �C for 12 hours. The

samples of zeolite confined nanostructured dinuclear ruthenium

clusters were bottled as black powders.

Characterization of zeolite confined nanostructured dinuclear

ruthenium clusters

Powder X-ray diffraction (XRD) patterns were recorded with

a MAC Science MXP 3TZ diffractometer using Cu Ka radiation

(wavelength 1.5406 A, 40 kV, 55 mA). Scanning electron

microscope (SEM) images were taken using a JEOL JSM-

5310LV at 15 kV and 33 Pa in a low-vacuum mode without metal

coating on an aluminium sample holder. Transmission electron

microscopy (TEM) was performed on a JEM-2010F microscope

(JEOL) operating at 200 kV. A small amount of powder sample

was placed on the copper grid of the transmission electron

microscope. Samples were examined at magnifications between

100 and 400k. The elemental analysis was recorded with an

energy dispersive X-ray (EDX) analyzer (KEVEX Delta series)

mounted on the Hitachi S-800 and modulated with TEM. The

nitrogen adsorption/desorption experiments were carried out at

77 K using a NOVA 3000 series (Quantachrome Instruments)

instrument. The sample was outgassed under vacuum at 573 K

for 3 h before the adsorption of nitrogen. The XPS analysis was

performed on a Physical Electronics 5800 spectrometer equipped

with a hemispherical analyzer and using monochromatic Al Ka

radiation (1486.6 eV, the X-ray tube working at 15 kV and

350 W, and pass energy of 23.5 eV). The FTIR spectrum was

This journal is ª The Royal Society of Chemistry 2009

taken from a KBr pellet on a Nicolet Magna-IR 750 spectrom-

eter using Omnic software. The Raman spectra of samples were

recorded on a Bruker RFS-100/S series Raman spectrometer

equipped with a Nd-YAG laser at 1064 nm using the FT-Raman

technique. X-Ray absorption spectra were recorded using

a fluorescence-yield collection technique at the Rigaku Corpo-

ration Tokyo Application Laboratory with a Mo target-LaB6

filament (40 kV, 50 mA) source attached to the Ge (840)

monochromator. The EXAFS data were examined by an

EXAFS analysis program, Rigaku (REX-2000) EXAFS. Fourier

transformation (FT) of k3-weighted normalized EXAFS data

was performed over the 3 A < k/A < 10.85 A range to obtain the

radial structure function. CN (coordination number of scatters),

R (distance between an absorbing atom and scatterer), and

Debye–Waller factor were estimated by curve-fitting analysis

with the inverse FT of the 0.9 < R/A < 3.0 range.

Typical example for zeolite confined nanostructured dinuclear

ruthenium cluster catalyzed aerobic oxidation of alcohols under

1 atm O2

In a typical experiment, 0.30 g of zeolite confined nanostructured

dinuclear ruthenium clusters (2.4 wt % Ru, corresponding to

0.071 mmol Ru) was put into a 250 mL reaction vessel (Parr Ins.

Model 4560). The reactor was evacuated to 200 Torr and filled

with pure O2 (99.5%) to 760 Torr, and this cycle was repeated

8 times. Then the reactor was heated to 80 � 1 �C and at this

temperature under O2 purging 0.1 mL benzyl alcohol (1 mmol) in

5 mL toluene was added via the tap of the reactor by using

a 10 mL gas-tight syringe, then the pressure of 760 Torr was

established and the reaction was started (t ¼ 0 min) by stirring

the mixture at 900 rpm under 760 Torr O2. The progress of the

reaction was followed by GC analysis of samples drawn from

the reaction solution using dodecane as internal standard. All of

the GC analyses were performed on a TRB-WAX column

(30 m � 0.25 mm � 0.25 mm) with a Shimadzu GC-2010

equipped with a FID detector.

Leaching test of zeolite confined nanostructured dinuclear

ruthenium clusters in the aerobic oxidation of benzyl alcohol

under 1 atm O2

After the complete oxidation of benzyl alcohol had been

achieved, the hot solution was filtered by suction filtration, the

filtrate of zeolite confined nanostructured dinuclear ruthenium

clusters was put into the reactor and the reactor was pressurized

to 1 atm with pure O2. The reaction was followed by GC. No

oxidation of benzyl alcohol was observed after 6 hours. Addi-

tionally, no ruthenium metal was detected in the hot filtrate

(�80 �C) by ICP which had a detection limit of 24 ppb for Ru.

Zeolite confined nanostructured dinuclear ruthenium cluster

catalyzed large scale aerobic oxidation of 1-phenylethanol under

1 atm O2

Zeolite confined nanostructured dinuclear ruthenium cluster

catalyzed 250 mmol scale oxidation of 1-phenylethanol was

performed in a Fischer-Porter pressure bottle modified with

Swagelock TFE-sealed quick connects and connected to an O2

line. Into an FP bottle 30.5 g of 1-phenylethanol (250 mmol) and

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100 mg of zeolite confined nanostructured dinuclear ruthenium

clusters (with a ruthenium loading of 1.5% wt, 0.0148 mmol Ru)

were added and the FP bottle was placed into an oil bath ther-

mostatted to 160 � 2 �C. The reaction was started (t ¼ 0 min) by

stirring the mixture at 900 rpm under 1 atm O2 and it was kept at

this pressure for the duration of the reaction. After 72 h the GC

analysis of the reaction mixture showed 82% conversion of

1-phenylethanol to acetophenone.

Fig. 2 (a) Low magnification and (b) high magnification SEM images of

ZC–Ru clusters, prepared from Ru3+-exchanged zeolite-Y with a ruthe-

nium content of 2.4% wt, taken on an aluminium sample holder without

metal coating.

Results and discussion

Preparation and characterization of zeolite confined

nanostructured dinuclear ruthenium clusters

The zeolite confined nanostructured dinuclear ruthenium clus-

ters were prepared by following a three step procedure: zeolite-Y

was first added to the aqueous solution of ruthenium(III) chlo-

ride in an amount depending on the degree of ion exchange,4 and

the suspension was stirred for 3 days at room temperature. At the

end of 72 hours the opaque supernatant solution became color-

less, indicating the completion of ion exchange. The isolated and

vacuum dried Ru3+-exchanged zeolite-Y sample was reduced by

sodium borohydride in aqueous medium at room temperature by

holding [NaBH4]/[Ru3+] > 500 to achieve complete reduction of

Ru3+ within the cavities of zeolite-Y. After filtering, copious

washing with water, and drying at 100 � 1.0 �C for 12 hours in

air ZC–Ru sample was bottled as black powder. The effect of the

preparation procedure on the integrity and crystallinity of the

host material zeolite-Y was investigated by XRD analysis. Fig. 1

depicts the XRD pattern of ZC–Ru along with those of zeolite-Y

and Ru3+-exchanged zeolite-Y samples. A comparison of the

XRD patterns clearly shows that the incorporation of ruth-

enium(III) ions into zeolite-Y and the formation of ZC–Ru

clusters cause no observable alteration in the framework lattice

and no loss in the crystallinity of zeolite-Y, since the peak posi-

tions and intensities are almost the same in all the patterns.

The morphology and composition of ZC–Ru were investigated

by TEM, HRTEM, SEM, EDX and ICP-OES analyses. Fig. 2

shows the SEM images of ZC–Ru with a ruthenium loading of

Fig. 1 Powder XRD patterns of (a) zeolite-Y, (b) Ru3+-exchanged

zeolite-Y with a ruthenium content of 2.4% wt, (c) ZC–Ru, (d) ZC–Ru

recovered from the fifth use in the aerobic oxidation of benzyl alcohol.

7114 | J. Mater. Chem., 2009, 19, 7112–7118

2.4% wt indicating that (i) there exist only crystals of zeolite-Y,

(ii) there is no bulk metal formed at observable size outside the

zeolite crystals, (iii) the method used for the preparation of

ZC–Ru does not cause any observable defects in the structure of

zeolite-Y, a fact which is also supported by the XRD results.

Indeed, the transmission electron microscopy (TEM) images

of the ZC–Ru sample show the distribution of ruthenium species

within the cavities of zeolite-Y (Fig. 3). The TEM-EDX spectrum

of ZC–Ru given in Fig. 3(c) shows that ruthenium is the only

element detected in addition to the zeolite framework elements

(Si, Al, O, Na) and Cu from the grid. Although no bulk ruthe-

nium metal is observed outside the zeolite crystals, confirmed by

Fig. 3 (a) High resolution TEM image of ZC–Ru, (b) high resolution

TEM image of ZC–Ru recovered from the fifth use in the aerobic

oxidation of benzyl alcohol at 80� 0.1 �C under 1 atm O2, (c) TEM-EDX

spectrum of ZC–Ru.

This journal is ª The Royal Society of Chemistry 2009

Fig. 4 The nitrogen adsorption-desorption isotherms of (a) zeolite-Y

and (b) ZC–Ru.

Fig. 6 Ru K-edge X-ray absorption near-edge structure (XANES)

spectra of ZC–Ru, RuCl3, RuO2 and Ru metal.

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XRD, SEM and TEM, the TEM-EDX and ICP-OES analyses

indicate the presence of ruthenium in the samples. This implies

that the ruthenium species are within the cavities of zeolite-Y.

Nitrogen adsorption-desorption isotherms of zeolite-Y and

ZC–Ru are given in Fig. 4 and both of them show type I shape,

characteristic of microporous materials.10 The micropore volume

and area were determined for zeolite-Y and ZC–Ru by the t-plot

method.11 On passing from zeolite-Y to ZC–Ru, both the

micropore volume (from 0.333 to 0.132 cm3/g) and the micropore

area (from 753 to 302 m2/g) are noticeably reduced. The

remarkable decreases in the micropore volume and micropore

area can be attributed to the encapsulation of ruthenium species

in the cavities of zeolite-Y. Furthermore, no hysteresis loop was

observed in the N2 adsorption-desorption isotherm of ZC–Ru

indicating that the three step procedure followed in the prepa-

ration of ZC–Ru doesn’t create any mesopores.

The XPS, Ru K-edge XANES and EXAFS studies provide

further insight into the local environment and oxidation state of

ruthenium in ZC–Ru. Fig. 5 shows the XPS spectra of ZC–Ru.

The survey spectrum given in Fig. 5(a) indicates that ruthenium

is the only element detected in addition to the zeolite framework

Fig. 5 (a) XPS survey scans, (b) 3d XPS spectra, and (c) 3p XPS spectra of

oxidation of benzyl alcohol (gray) at 80 � 0.1 �C under 1 atm O2.

This journal is ª The Royal Society of Chemistry 2009

elements, which supports the finding by TEM-EDX (vide supra).

The XPS spectrum of ZC–Ru12,13 shows two prominent bands at

283.3 and 466.7 eV, readily assigned to Ru(III) 3d5/2 (Fig. 5b)

and Ru(III) 3p3/2 (Fig. 5c), respectively, by comparison with the

literature values for ruthenium(III) chloride14 and compounds

such as K2[RuCl5(H2O)].15 Additionally, the Ru K-edge X-ray

absorption near-edge structure (XANES) spectrum of ZC–Ru

(Fig. 6) is almost identical to that of RuCl3. These observations

indicate unequivocally the existence of ruthenium in the oxida-

tion state of 3+ in ZC–Ru species.

The Fourier transform (FT) of the k3-weighted extended X-ray

absorption fine structure (EXAFS) spectrum of ZC–Ru sample is

depicted in Fig. 7(a). First of all, this spectrum shows clearly the

absence of RuO2 in the ZC–Ru sample, as contiguous Ru–O–Ru

bonds would give peaks at around 3.5 A.16,17

The inverse FT of the main peaks in the spectrum was well

fitted, by the use of four Ru–O bonds (Fig. 7(b)) with interatomic

distances (R) of 1.97 and 2.3 A, and a single Ru–Ru shell

parameter (Fig. 7(c)) with an interatomic distance (R) of 2.66 A

as summarized in Table 1. The distance of the shortest

ZC–Ru (black) and ZC–Ru recovered from the fifth use in the aerobic

J. Mater. Chem., 2009, 19, 7112–7118 | 7115

Fig. 7 (a) FT magnitude of k3-weighted EXAFS of ZC–Ru compared with those of Ru metal and RuO2; curve fitting analysis of the inverse FT of the

peaks with (b) 0.9 < R(A) < 2.1 in (a) using four Ru–O shell parameters, and (c) 2.0 < R(A) < 3.0 in (a) using one Ru–Ru shell parameter; (d) local

structure of ZC–Ru obtained from Ru K-edge EXAFS analyses.

Table 1 Curve fitting results of Ru K-edge EXAFS analyses of ZC–Rua

Entry Shell CNb R (�A) Ds/Ac

1 Ru–O 2.70 1.97 0.00452 Ru–O 0.70 2.30 0.00303 Ru–Ru 1.40 2.66 0.0049

a The region of 0.9–3.0 A was inversely Fourier transformed.b Coordination number. c Debye–Waller factor.

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Ru–O bond (1.97 A) is slightly longer than that of Ru]O

(1.85 A),17,18 and can be assigned to Ru–OH species as observed

in RuHAP–g-Fe2O3 (1.95 A).16† The Ru–O distance of 2.30 A is

very close to that of the Ru–O(zeo) (2.26 A) interaction observed

in the case of [Ru6(CO)18]2�/Na56X.19

The peak observed at 2.66 A corresponds to the intermetallic

pair; it appears at the same distance as the Ru–Ru pair in the FT

of bulk ruthenium (Fig. 7(a)). Conclusively, the dinuclear

† The FTIR and Raman spectra of ZC–Ru show the v(OH) stretchingband in the region of 3400–3700 cm�1.

7116 | J. Mater. Chem., 2009, 19, 7112–7118

ruthenium(III) clusters are encapsulated within the framework of

zeolite-Y and each ruthenium center is surrounded by three

hydroxyl ligands and one oxygen of the zeolite framework

(Fig. 7(d)).

The catalytic application of zeolite confined nanostuctured

dinuclear ruthenium clusters in the aerobic oxidation of alcohols

The ZC–Ru samples were tested as catalysts in the aerobic

oxidation of various alcohols at 80 �C under 1 atm O2 pressure

(Scheme 1) and representative results are listed in Table 2. In

general, ZC–Ru shows high catalytic activity and selectivity in

the aerobic oxidation of alcohols to carbonyl compounds.

All the benzylic and allylic alcohols (entries 1–6) were con-

verted to the corresponding carbonyl compounds in >99%

selectivity. The oxidation of benzyl alcohol to benzaldehyde can

be achieved within 2.5 hours even in air instead of pure O2 (entry

1). Additionally, it can catalyze the same reaction even at room

temperature, with 45% conversion and >99% selectivity in 24 h.

Unactivated alcohols were also smoothly oxidized to the

corresponding carbonyl compounds in high conversion and

This journal is ª The Royal Society of Chemistry 2009

Scheme 1 ZC–Ru catalyzed aerobic oxidation of alcohols to carbonyl

compounds at 80 �C under 1 atm O2.

Scheme 2 ZC–Ru catalyzed aerobic oxidation of 1-phenylethanol to

acetophenone at 160 �C under 1 atm O2.

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selectivity, though a longer reaction time is needed (entries 7 and

8). The ZC–Ru clusters also catalyze the selective oxidation of

2-pyridinylmethanol and 2-thiophenylmethanol to the corre-

sponding aldehydes in high yields (entries 9 and 10). The isol-

ability and reusability of ZC–Ru, two crucial measures in

heterogeneous catalysis, were tested in the aerobic oxidation of

benzyl alcohol. After the complete oxidation of benzyl alcohol,

ZC–Ru was isolated as black powder by suction filtration,

washed with water, and dried under vacuum at room tempera-

ture. The dried black sample of ZC–Ru can be bottled and stored

under ambient conditions. Furthermore, when reused in toluene,

ZC–Ru is still an active catalyst in the oxidation of benzyl

alcohol, retaining >99% of the initial catalytic activity even at the

fifth run (entry 1). Taking all the results together one can

conclude that ZC–Ru is isolable, bottleable, redispersible, and

repeatedly usable as an active catalyst in the aerobic oxidation of

Table 2 Aerobic oxidation of alcohols catalyzed by zeolite confined nanostr

Entry Substrate Product

1

2

3

4

5

6

7

8

9

10

a Alcohol (1 mmol), ZC–Ru (300 mg), toluene (5 mL), 80 �C, 1 atm O2. b In ausing an internal standard method. d The reaction was performed in air insteunder the same conditions as in d.

This journal is ª The Royal Society of Chemistry 2009

alcohols. That no Ru was detected in the filtrate by the ICP

technique (with a detection limit of 24 ppb for Ru) confirms the

retention of ruthenium within the zeolite (no ruthenium passes

into the solution during the suction filtration). A control exper-

iment was performed to show that the oxidation of benzyl

alcohol is completely stopped by the removal of ZC–Ru from the

reaction solution. It is also noteworthy that XRD (Fig. 1d), TEM

(Fig. 3b) and XPS (Fig. 5) analyses of the recovered ZC–Ru at

the end of the fifth use in the oxidation of benzyl alcohol reveal:

(i) no loss in the crystallinity of the host material, (ii) no sintering

or migration of ruthenium clusters out of the cavities of zeolite-

Y, and (iii) no reduction of Ru3+ to Ru2+ or Ru(0).

The applicability of ZC–Ru (0.006% mol Ru) to solvent free

catalysis was tested in the oxidation of neat 1-phenylethanol

uctured dinuclear ruthenium clustersa,b

Time (h) Conversion (%)c

1 1002.5d 100

24e 452.5f 100

4 100

1 98

2 100

1.5 100

2 100

6 97

8 95

3 95

3 92

ll experiments the selectivity was found to be >99%. c Determined by GCad of 1 atm O2. e The reaction was performed at 25 �C. f At the fifth use

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(0.25 mol corresponding to a maximum turnover number of

17860) at 160 �C (Scheme 2). ZC–Ru provide 13800 total turn-

overs per ruthenium in the oxidation of neat 1-phenylethanol

over 72 hours before deactivation and a turnover frequency value

up to 340 h�1.

Conclusions

The main findings of this work as well as implications or

predictions of our findings can be summarized as follows.

(1) ZC–Ru has been prepared, for the first time, by using an

easy three step procedure. The characterization by means of ICP-

OES, XRD, XPS, Ru K-edge XANES and EXAFS, TEM,

HRTEM, TEM/EDX, SEM, FTIR spectroscopy and N2

adsorption-desorption technique showed the formation of

nanostructured dinuclear ruthenium(III) centers each coordi-

nated to three hydroxyl groups and one oxygen of the zeolite

framework whilst keeping the zeolite framework intact.

(2) ZC–Ru provides exceptional catalytic activity and selec-

tivity in the aerobic oxidation of both activated and unactivated

alcohols, which may have a carbon-carbon double bond or

a heteroatom, such as sulfur or nitrogen, under mild conditions by

using 1 atm O2 or air without using any oxidizing agents, additives

or even solvent. Additionally, ZC–Ru is highly stable in terms of

crystallinity, morphology and oxidation state of ruthenium,

which makes it bottleable and reusable. As expected, the bottled

and reused ZC–Ru retains >99% of its initial catalytic activity

even at the fifth run in the aerobic oxidation of benzyl alcohol.

(3) Furthermore, among the reported ruthenium catalysts20

ZC–Ru provides record catalytic activity and lifetime with TOF

and TTON values of 340 h�1 and 13800, respectively in the

solvent free oxidation of 1-phenylethanol.

(4) The high catalytic activity, easy preparation, isolability,

bottleability, and reusability of ZC–Ru raise the prospect of

using this type of simply prepared material for the aerobic

oxidation of alcohols in industrial applications as well as in small

scale organic synthesis.

Acknowledgements

Partial support by the Turkish Academy of Sciences is gratefully

acknowledged. We thank Keigo Nagao and Rigaku Corporation

Tokyo application laboratory for the XAFS measurements and

analyses. Mehmet Zahmakıran thanks TUBITAK (2214-

Research Fellowship) and all the members of the Compact

Chemical Process Research Team in the National Institute of

Advanced and Industrial Science and Technology (AIST) in

Tsukuba.

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