DOI: 10.1002/chem.201404949
Full Paper
&
Heterogeneous Catalysis
Graphene Oxide Supported Molybdenum Cluster: First
Heterogenized Homogeneous Catalyst for the Synthesis of
Dimethylcarbonate from CO2 and Methanol
Subodh Kumar,[a] Om P. Khatri,[a] Stꢀphane Cordier,[b] Rabah Boukherroub,[c] and
Suman L. Jain*[a]
Abstract: The octahedral molybdenum cluster-based com-
studies. The developed material was used for the synthesis
of dimethyl carbonate by reduction of carbon dioxide. The
pound, Cs2Mo6Bri8Bra was immobilized on graphene oxide
6
(GO) by using a facile approach. High resolution transmission
electron microscopy results revealed that molybdenum clus-
ters were uniformly distributed on the GO nanosheets.
Cs2Mo6Bri8Bra6 was attached to the GO support via chemical
synthesized catalyst, that is, GO–Cs2Mo6Bri8Bra , exhibited
x
higher catalytic efficiency than its homogeneous analogue
without using dehydrating agent. The catalyst was found to
be efficiently recyclable without significant loss of catalytic
activity.
interaction between apical ligands of Mo6Bri8Bra cluster
6
units and oxygen functionalities of GO, as revealed by XPS
Introduction
method to produce DMC, yet the use of CO and the expensive
nature of catalyst makes the process undesirable.[5] In recent
years, much emphasis has been given to the synthesis of DMC
from the direct reaction of CO2.
Carbon dioxide (CO2) is one of the major causes of climate
change because of its continuous accumulation in the atmos-
phere.[1] Many approaches have been proposed to reduce the
level of CO2 in the atmosphere. Direct conversion of CO2 into
value-added chemicals has turned out to be promising from
both environmental and economical viewpoints.[2] Among the
various chemicals synthesized from CO2, dimethylcarbonate
(DMC), a simplest organic carbonate, has attracted considera-
ble attention due to its versatile applications such as an envi-
ronmentally benign substitute to highly toxic and corrosive
carbonylating and methylating agents phosgene and dimethyl-
sulfate,[3] as a precursor to polycarbonate resin, an electrolyte
of lithium ion batteries, as an additive in gasoline for octane
boosters, etc.[4] Conventionally, DMC is synthesized by reaction
of phosgene with methanol, which is highly toxic and corro-
sive. The oxidative carbonylation of methanol is an alternate
In this context, a number of homogeneous and heterogene-
ous catalysts have been explored.[6] However, poor per-
formance, need of dehydrating agent and unsatisfactory yield
of DMC still leave much scope to develop an efficient catalyst
system for enhancing the DMC yield and selectivity. Recently,
Medina et al. reported Mg-Al hydrotalcite-silica lyogels to be
superior catalysts for the direct synthesis of DMC from CO2 and
methanol. However, tedious synthesis, leaching and deactiva-
tion of catalyst limit its scope for application perspectives.[7]
[(Mo6Li8)La6]2À molybdenum octahedral cluster units are
nanosized anionic moieties based on octahedral hexanuclear
Mo6 clusters (Figure 1), where Li and La are the inner face
capped and apical ligands, respectively. The size of one
[Mo6Br14]2À cluster unit is approximately 1 nm according to the
lattice parameter of the starting Cs2[Mo6Br14] cluster-based pre-
cursor.[8] The latter compound as homogeneous catalyst, could
afford DMC from CO2 and methanol. However, non-recyclability
of cluster compounds, could make the catalytic process expen-
sive. Furthermore, it requires dehydrating agents for the reac-
tion to proceed efficiently in the forward direction. Thus, we
intended to immobilize clusters onto solid support to make
them recyclable and reusable.
[a] S. Kumar, Dr. O. P. Khatri, Dr. S. L. Jain
Chemical Sciences Division, CSIR-Indian Institute of Petroleum
Mohkampur, Dehradun-248005 (India)
[b] Dr. S. Cordier
Institut Sciences Chimiques de Rennes
Universitꢀ de Rennes 1UR1-CNRS 6226
Equipe Chimie du Solide et Matꢀriaux
Campus de Beaulieu, CS 74205, 35042 Rennes Cedex (France)
Recently, graphene oxide (GO) and reduced GO have been
established as promising host materials for heterogenization of
various catalytically active transition-metal clusters, metal oxide
nanoparticles, active metal complexes, and organic functionali-
ty catalysts for efficient chemical transformations.[9,10] The re-
markable properties of GO such as high specific surface area,
[c] Prof. R. Boukherroub
Institut de Recherche Interdisciplinaire (IRI, USR CNRS 3078)
Universitꢀ Lille 1, Parc de la Haute Borne, 50 Avenue de Halley
BP 70478, 59658 Villeneuve d’Ascq (France)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201404949.
Chem. Eur. J. 2014, 20, 1 – 8
1
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ