Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Biocompatible and recyclable amino acid binary catalyst for efficient
chemical fixation of CO2
a
b
b
b
a,
b,
Zifeng Yang , Jian Sun , Weiguo Cheng , Jinquan Wang , Qian Li ⁎, Suojiang Zhang ⁎⁎
a
School of Chemistry and Chemical Engineering Henan University, Kaifeng 475001, PR China
Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences,
b
Beijing 100190, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 April 2013
Received in revised form 22 June 2013
Accepted 12 July 2013
Available online 23 July 2013
In this work, the cycloaddition reactions of CO with various epoxides to form five-membered cyclic carbonates
catalyzed by an efficient amino acid based biocompatible catalyst were investigated. It was found that the activity
of amino acid could be obviously enhanced in the presence of alkali metal salts, and the L-tryptophan catalytic
system was the most efficient among the catalysts employed. Based on the result, a possible mechanism for
the synergetic effect of catalyst was proposed. The process reported here represents a simple, ecologically
safer, cost-effective route to cyclic carbonates with high product quality, as well as easy catalyst recycling.
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Keywords:
Amino acid
©
2013 Elsevier B.V. All rights reserved.
Cyclic carbonates
Carbon dioxide
Chemical fixation
Synergistic catalysis
1
. Introduction
salts could be used as catalyst for the synthesis of cyclic carbonates
together with natural products, such as β-cyclodextrin, cellulose,
and lecithin [18–20]. Although the reaction process is ecologically
safe, high pressure and long time are unsatisfied for this kind of cat-
alyst, which still needs to be improved. The development of effi-
cient, cheap, ecologically safe, and recyclable catalysts for a
reaction under green reaction conditions is still a very attractive
topic.
In recent years, using amino acids as catalysts have gained much
interest [21,22]. Amino acids are natural, green, non-toxic chemicals
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which contain active N (e.g. \NH , \NH) and strong hydrogen bonding
(e.g. \COOH or \OH) in the molecule. He et al. [8] reported that amino
acid and epoxide could form an amino acid-epoxide complex through
hydrogen bonding, which could activate the epoxide. Several groups in-
cluding us reported that the synergistic effect between halide anion and
hydrogen bond could promote the cycloaddition reaction [19,23,24].
Owing to amino acids containing strong hydrogen bonding, the addi-
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Chemical conversion of carbon dioxide (CO ) into useful organic
compounds has attracted much attention in recent years [1], because
CO is not only a renewable, abundant and nontoxic resource, but also
a primary greenhouse gas responsible for climate change [2]. It has
been well known that the CO fixation with epoxide to produce five-
membered cyclic carbonates is an important contribution from the
viewpoint of resource utilization [3].
In past decades, various homogeneous and heterogeneous cata-
lysts have been developed to catalyze the reaction, such as metal
oxides [4], alkali metal salts [5,6], transition metal salen complexes
2
2
[
7], functionalized ionic liquids [8,9], functionalized polymers [10,11],
silica-supported ionic liquids [12,13], ion-exchange resin-supported
gold nanoparticle [14], magnetic nanoparticle-supported porphyrin
[
15], choline chloride and urea supported on molecular sieves [16],
biopolymer-supported catalyst [17], and so on. Among the above
catalysts, alkali metal salts are one of the most important type
of catalysts for the reaction due to they are cheap, stable and envi-
ronmentally friendly [5,6]. Han et al. reported that alkali metal
2 2
tional \NH group in amino acid was proposed to activate CO
[25–30]. Therefore, we envisioned that alkali metal halide and amino
acids could be utilized as efficient complex catalysts under solvent-
free conditions for the cycloaddition reaction. Herein, a novel catalytic
system prepared by combining one of five typical structure amino
acids, glycine, L-aspartic acid, L-threonine, L-histidine, and L-tryptophan
(
Scheme 1) with potassium halide was examined for the CO
2
chemical
fixation. The effects of various parameters, such as catalyst, catalyst
⁎
Corresponding author. Tel./fax: +86 10 82627080.
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amount, reaction time, temperature and CO pressure on the reaction
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were investigated.