Full Paper
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um chloride solution (1.45m) and a salt of the second metal (alumi-
nium nitrate nonahydrate (99.9%, Sigma Aldrich), chromium chlo-
ride hexahydrate (96%, Sigma Aldrich) or iron (III) chloride hexahy-
drate (Aldrich)) were dissolved in the desired proportions in dime-
thylformamide (DMF; Acros, 98%, 10 mL). In each case the molar
ratio of total trivalent metal cations to BTC was kept at 3:2 and
molar ratios of Sc:M of 100:0, 80:20, 60:40, 60:40, and 80:20 were
used, as well as others in some cases. The ratio of BTC to solvent
DMF was kept at 2:600. In a typical preparation of a material of
nominal MIL-100(Sc ,Fe ) composition, benzene-1,3,5-tricarboxylic
acid (BTC, Aldrich, 95%, 0.0908 g, 0.43 mmol), scandium chloride
solution (1.45m, 0.39 mmol, 0.27 mL), and iron (III) chloride hexahy-
drate (Aldrich, 0.26 mmol, 0.0701 g) were dissolved in dimethylfor-
mamide, DMF (Acros, 98%, 10 mL). The reaction mixtures were
heated in a Teflon-lined steel autoclave at 383 K for 24 h. For the
MIL-100(Sc,Fe)XS series, the molar ratio of total trivalent metal cat-
ions to BTC was kept at 3:2 and molar ratios of Sc:Fe of 2:2–5
were used. The ratio of BTC to solvent DMF was kept at 2:600.
cle size 35–70 mm. H NMR, C NMR, F NMR, and P NMR were
carried out using a Bruker Avance 400 spectrometer at 400 Hz or
Bruker Avance 300 spectrometer at 300 Hz. Chemical shift informa-
tion for each signal is given in part per million (ppm) relative to tri-
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methylsilane (TMS). Chemical shifts for F are relative to CFCl and
P relative to phosphoric acid. Methanol-washed, thermally acti-
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vated MOF catalysts were used in a series of Lewis acid catalyzed
Friedel–Crafts reactions of 2-methylindole and related compounds
with trifluoroacetaldehyde ethyl hemiacetal to give alcohols. The
oxidation of these alcohols was performed over MOFs using tert-
butylhydroperoxide to give ketones, and for selected MOFs, the
tandem, one-pot reaction was also performed. The amount of MOF
catalyst used was 5 mol%, unless stated otherwise, calculated as
the molar percentage of the available metal cation (Sc, Fe, Cr, Al,
or Cu), of the reactant molecule. (For MIL-100 materials two out of
three metal cations per trimer were considered available, with one
in three coordinated by an anion). 100% conversion therefore re-
lates to a turnover number of 20. Conversions were calculated for
all reactions involving ethyl trifluoropyruvate or trifluoroacetalde-
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The resulting solids were washed with ethanol and water and
dried at 608C. Product identification was carried out using powder
X-ray diffraction (PXRD). PXRD patterns were collected for MOFs
using PANalytical Empyrean and STOE STADI P diffractometers
using CuKa1 X-radiation (l=1.54056 ꢂ). Adsorption isotherms for
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hyde ethyl hemiacetal using F{ H} NMR using 1-fluoronaphtha-
lene as an internal standard ( H NMR was also measured for com-
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pleteness), and in these reactions no peaks other than reactant,
product, and internal standard were observed, except for the car-
bonyl ene reaction, when the hydrated reactant ethyl-3,3,3-tri-
fluoro-2,2-dihydroxypropanoate was sometimes observed. For the
conjugate addition of 2-methylindole to methyl vinyl ketone, con-
N on the MIL-100 samples were obtained at 77 K using a Micro-
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meritics Tristar II 3020. Prior to measurement of the isotherms, the
samples were washed with methanol and activated under vacuum
at 1508C for 5 h. EDX measurements were obtained by a JEOL
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versions to product were measured by H NMR. For some reactions
the product was isolated and its identity and purity confirmed by
NMR, MS, and elemental analysis. Detailed examples are given in
the Supporting Information.
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600 SEM with an Oxford INCA Energy 200 EDX system. Elemental
analyses were performed on organic compounds and metal–organ-
ic frameworks by Elemental Analysis Service, London Metropolitan
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University, London, UK. Al and Sc NMR spectra were obtained
using a Bruker Avance III 600 MHz spectrometer, equipped with
a wide-bore 14.1 T superconducting magnet, at Larmor frequencies
Acknowledgements
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of 156.4 MHz for Al and 145.8 MHz for Sc. C NMR spectra were
obtained using Bruker Avance III 400 MHz spectrometer,
equipped with a wide-bore 9.4 T superconducting magnet, at
We thank Johnson Matthey and the EPSRC for an Industrial
CASE award to L.M. We gratefully acknowledge the IAESTE UK
for a scholarship to B.E. and we also thank the Leverhulme
Trust (F/00 268/BJ), EPSRC (EP/J501542/1), and the EaStCHEM
Research Computing Facility. We are grateful to Diamond Light
Source for provision of beamtime for XAS and to Dr. Giannan-
tonio Cibin for assistance in measuring the data on station
B18. We gratefully acknowledge Dr. Alexandre Vimont at the
Laboratoire Catalyse et Spectroschemie, ENSICAEN, Caen for
help with measurement and analysis of the IR spectra. We
thank all the technical staff at the University of St Andrews
School of Chemistry for their assistance.
a
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Larmor frequencies of 400.16 MHz for H and 100.6 MHz for C.
Powdered samples were packed into 4 or 2.5 mm ZrO rotors and
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rotated at MAS rates between 12.5 and 30 kHz. Chemical shifts are
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given relative to TMS for C, 1m Al(NO ) (aq) for Al and 0.2m
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ScCl (aq) for Sc. For C, spectra were acquired using cross-polari-
sation, with a contact pulse (ramped for H) of 1.5 ms duration and
H decoupling (SPINAL64) was applied throughout acquisition.
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TEM images of MIL-100(Sc Fe )XS were produced using a Jeol
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JEM 2011 HRTEM with an accelerating voltage of 200 kV. The sam-
ples were prepared by grinding the powder sample with acetone
and depositing the solution on a Cu grid. HKUST-1(Cu) (Cu BTC )
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was prepared according to a published synthesis and characterised
by PXRD (Supporting Information). Its BET surface area, determined
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ꢀ1
Keywords: bifunctional catalysts · heterogeneous catalysis ·
iron · scandium · tandem catalysis
by N adsorption at 77 K, was 965 m g .
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For all of the catalytic reactions, chemicals were purchased from
commercial suppliers. Dry solvents were used in reactions that
[
were carried out under N . Electrospray ionisation mass spectrosco-
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py was performed with a Micromass LCT spectrometer, operated
by Mrs Caroline Horsburgh at St Andrews University, or at the
ESPSRC National Mass Spectrometry Service Centre, Swansea Uni-
versity, by using Waters ZQ4000, Thermofisher LTQ Orbitrap XL and
Finnigan MAT 900 XLT Instruments. Thin layer chromatography was
carried out on pre-coated 0.2 ꢂ Machery-Nagel Polygram SIL G/
UV254 silicon plates. Absorption under UV light was visualised as
well as thermal decomposition after immersion in aqueous solu-
tion of potassium permanganate if required. Column chromatogra-
phy was performed using Davisil silica gel Fluorochem 60 ꢂ, parti-
[
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Chem. Eur. J. 2014, 20, 1 – 14
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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Mitchell, Laura
