Current advances in heterogeneous catalysts for the

Current Opinion in Green and Sustainable Chemistry 3 (2017) 1e10

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Review article

Current advances in heterogeneous catalysts for the synthesis of cyclic carbonates from carbon dioxide Vitthal B. Saptal, Bhalachandra M. Bhanage* Department of Chemistry, Institute of Chemical Technology, Mumbai 400 019, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 10 September 2016 Received in revised form 21 October 2016 Accepted 31 October 2016 Available online 3 November 2016

The novel heterogeneous catalysts are highly demanded to perform the cycloaddition reaction of carbon dioxide with epoxide to synthesize the cyclic carbonates. The heterogeneous catalysts are more preferred than homogeneous catalysts due to the easy post reaction separation, easy to recycle, high stability and cost effective nature. In this review, we have summarized the current research progress in heterogeneous catalysis for the cycloaddition of carbon dioxide (CO2) to synthesis of cyclic carbonates. Recent advances in the design of the heterogeneous catalysts and the understanding to the role of catalysts in reaction process are summarized and discussed. © 2016 Elsevier B.V. All rights reserved.

1. Introduction The concentration of CO2 on the earth surface is increasing day by day and become threats to the living system. The CO2 is kinetically as well as thermodynamically stable; having electrophilic characteristics at carbon atom and nucleophilic characteristics on oxygen atom [1a].The catalytic fixation of CO2 with epoxides to cyclic carbonates is considered as an artificial fixation of CO2 to synthesize the value added chemicals (Scheme 1). This reaction having some advantages for example it provides 100% atom economy, non-toxic nature can replaces the phosgene and CO as poisonous gases and utilizes the CO2 to as a waste material generated from the industries and transportations. The cyclic carbonates utilized as monomers in synthesis of biocompatible polymers, electrolytes in lithium ion batteries, aprotic solvents and synthesis of linear dialkyl carbonates [1]. Various homogeneous catalytic systems with or without metal have been well established for this reaction [2].In last few decades, the heterogeneous catalytic systems are getting intense attention to synthesis of carbonates from CO2 and epoxides. 2. Metal organic frameworks (MOFs) MOF are organic inorganic hybrid material and greatly

* Corresponding author. E-mail addresses: [email protected], (B.M. Bhanage). http://dx.doi.org/10.1016/j.cogsc.2016.10.006 2452-2236/© 2016 Elsevier B.V. All rights reserved.

[email protected]

crystalline, stable, porous, structurally tunable, and shows high affinity towards CO2, hence, considered as most prominent candidate for the CO2 fixation (Table 1) [3].The MOFs containing ligand (linkers) and metal ions (Fig. 1) with polymeric structers, they are highly crystalline and easily separable from the reaction mixture. Recently, the triazole based MOF are shown high activity towards size and shape selective synthesis of carbonates [4a], Han et al. utilized polyoxometalate-based homochiral MOFs (POMOFs) for auto-tandem epoxidation/cycloaddition catalytic reaction of light olefin to synthesize the enantiomerically pure cyclic carbonates [4b]. Indium based, 1,2,4-H3btc withpiperazinebased MOF having acid base nature shows excellent catalytic activity towards the carbonates [5].The ZnII and CuIIMOFscontaining free amine functional group shows high activity for carbonate synthesis as well as click reactions and three component coupling reactions [6].The immobilized IL on ZeoliticImidazolate Framework (ZIF) IL-ZIF-90 (Scheme 2), acts as additive free catalyst for synthesis of carbonates [7].The Zn-Glu MOF derived L-glutamic acid as ligand for the synthesis of carbonates and oxazolidinones [8].Han et al. synthesized porous MOF using the 4,40 ,400 -s-triazine-1,3,5-triyl-tri-paminobenzoic as tritopic carboxylate and DABCO as ligands for dual-walled icosahedral cage like MOF assembled by combining zinc paddlewheel units shows high TON [9]. Zhou et al. synthesized Ni-TCPE1 MOF and utilized for carbonates synthesis with high TON [10]. The MIL-101-N(n-Bu)3Br and MIL-101-P(n-Bu)3Bras a bifunctional MOF combined with ILs also utilized to synthesize propylene carbonates without using the co-catalyst [11]. The functional group such as eCOOH group in {Cu(Hip)2(Bpy)}n MOF for the

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V.B. Saptal, B.M. Bhanage / Current Opinion in Green and Sustainable Chemistry 3 (2017) 1e10

Scheme 1. Classification of heterogeneous catalysts for the synthesis of cyclic carbonates in this review. Table 1 Conditions utilized for the synthesis of cyclic carbonates using MOF as catalysts. Entry

MOF

Active sites

Temp. ( C)

Pressure (Bar)

Time (h)

Yield (%)

Recycle

Reference

1 2 3 4 5 6 7 8 9 10 11 12 13

{Cu4[(C57H32N12) (COO)8]}n and HKUST-1 POMOFs In2(OH)(btc)(Hbtc)0.4(L)0.6$3H2O LCu’ IL-ZIF-90 ZnGluMOF Zn-polyhedral MOF Ni-TCPE1 MIL-101-N(n-Bu)3Br and MIL-101-P(n-Bu)3Br CHB(M) and CHB(s) MMCF-2 FJI-H6 and FJI-H7 TMOF-1

Triazole and Metal Pyrrolidine Piperazine Amine IL Zinc-glutamate DABCO Proline IL eCOOH Azamacrocycle Ligand Porphyrin Organosulfonate

RT 50 80 120 120 RT 100 100 80 120 RT RT RT

1 atm 5 20 20 10 10 1 atm. 10 20 12 1 atm. 1 atm. 1 atm.

48 48 4 12 3 24 16 12 8 6 48 60 48

96 92 93 50 97 94 99 97 99 95 95 66 99

5 e 5 e 5 4 6 4 3 5 e e 5

[4a] [4b] [5] [6] [7] [8] [9] [10] [11] [12] [13a] [13b] [13c]

cycloaddition reaction of CO2 and allylgycidyl ether to glycidal carbonates [12].The decoration of MOF-505 to MMCF-2 by using azamacrocycle shows excellent activity to carbonates at mild pressure and temperature [13a].Zirconium and Hafnium based MOF containing porphyrinligands are highly porous in nature and shows high chemical and water stability also found highly effective for this reaction [13b]. Very recently the sulfonate based MOF also synthesized applied for this reaction at mild reaction conditions [13c].

3. Ionic liquids In case of CO2 capture and conversion the ionic liquids (ILs) are considered as one of the promising material due toits characteristics(Fig. 2a) [14].ILs are tunable in nature and having negligible vapour pressure, low toxicity easy to synthesize and highly stable in nature. Among them cross-linked polymeric and polymer supported ILs (PSILs)are highly stable, containing functional imidazolium, ammonium, phosphonium and pyridinium

Fig. 1. (a)Representative structure of MOF containing the ligand (linkers) and metalions and (b) structure of MOF-5.


Scheme 2. Synthetic method for the synthesis of IL-ZIF-90.

Fig. 2. (a) Structures of polymer supported ILs with hydroxyl functional group (b) and (c)Synthetic pathway for the PILs [22].

Fig. 3. Hydroxyl functionalized ILs supported on silica as well as polymer.

3

4


Table 2 Conditions utilized for the synthesis of cyclic carbonates using the ILs. Entry

ILs

Temp. ( C)

Pressure (Bar)

Time (h)

Yield (%)

Recycle

Reference

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

[DABCOePDO][I] Silica and polymer supported PSIL-NTf-2 TBB-Bpy@Salen-Co POM3-IM PAD-3 MPILs [(CH2CH2OH)Bim]ZnBr3 NH2eZn/SBA-15 UDIL GO-HEIMBr GO-DMEDA-I GO-[SmIm]I GP KCC-1/IL/HPW [Ch][His] EG/HEBimBr

110 90 100 60 120 110 110 120 150 130 120 120 140 90 120 70 120

20 10 8 10 10 10 10 20 30 15 20 20 20 10 15 1 atm. 20

3 2 6 6 8 0.5 4 2 12 3 4 4 4 3 2 30 4

99 99 94 100 92 99 98 81 99 97 99 97 96 99 98 92 96

7 13&8 8 5 6 5 6 5 5 5 7 5 4 e 10 5 4

[16] [17] [18] [19a] [19b] [20] [21] [23] [24] [25] [26a] [26b] [27] [28a] [28b] [28c] [28d]

Fig. 4. (a) Synthetic method for the synthesis of PAD-3 IL and (b) reaction mechanism for the synthesis of carbonates catalysed by PAD-3.


5

Fig. 5. (a) structure of urea based IL and (b) reaction mechanism for the cycloaddition reaction catalysed by urea based IL.

Fig. 6. (a) Schematic representation of the synthesis of GO-HEMBr and(b) KCC-1/IL/HPW NPs.

with hydrogen bond donor (HBD) are mainly focused in recent days [15]. We synthesized various DABCO based bifunctional PSILs for the multitask conversion, this ILs are especially highly active for the cyclic carbonates (Fig. 2b) [16].Hydroxyl functional supported on silica and polymer shows high recyclability (Table 2, entry 2) [17] as well as imidazolium based ILs also active shows excellent catalytic

activity as well as recyclability [18] (see Fig. 3). While, recently the cross linked polymer containing imidazole ILs such as TBB-Bpy@Salen-Co [19a], POM-IM [19b], PAD-3 (Fig. 4) [20], MPILs [21], and PILs (Fig. 2b) [22] are highly active at mild reaction conditions. Sun et al. reported various ILs system for the synthesis of carbonates such as hydroxyl functionalized Zinc based

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phosphorous based ILs also shows high reactivity for cyclic carbonates [28]. The fibrous nano-silica supported heteropolyacidbased ILs (KCC-1/IL/HPW) also shows high activity and recyclability up to 10 cycles towards the carbonates at mild conditions (Fig. 6b) [28b].Very recently, we synthesized bifunctional ILs derived from biorenewable sources such as choline and amino acids and applied for this reaction, the presence of hydroxyl functional as well as the amine functional group helps to activate the epoxide and carbon dioxide effectively at the mild reaction conditions [28c]. The systematic effect of HBD catalysts to activation of epoxide ring was investigated by Sun et al. by using various ILs and ethylene glycol as HBD [28d]. 4. Organocatalysts The use of organocatalysts to synthesize the chemicals are considered as cutting edge technology due to safe, non-toxic, and sustainable nature of organocatalysts as compared to metal catalyst [14c,29].Recently, Hirose et al. used pyridine alcohol and tetrabutylammonium Iodide (TBAI) as a bifunctional catalytic system [30].Kleijutilized tannic acid TA/NBu4X [31] and Chen used the sugarcane bagasse/KI [32], as a green and sustainable HBD catalyst for the synthesis of carbonates andoxazolidinones. Fig. 5. 5. Other porous materials Fig. 7. (a) Hydroxyl functionalized phosphonium ILs (b)immobilized IL on functionalgraphene oxide (F-GO).

ILs [23], [urea-Zn]I2 eutectic mixture [24], urea derivative-based ionic liquids (UDILs)for the synthesis of carbonates (Fig. 5) [25] Immobilized ILs on carbon material such as GO-HEIMBr (Fig. 6a) [26a],graphene oxide grafted with quaternary ammonium salts bearing terminal amino groups [26b] and GO-[SmIm]X [27] synthesized and applied for this reaction. Hydroxyl functionalized

Beside the homogeneous but recyclable catalysts [33],huge number of porous heterogeneous catalysts have been developed recently. The nitrogen rich porous azo-linked frameworks (PAFs) supported ZnBr2 catalyst [34] and mesoporous o-hydroxyazobenzene POP with zinc shows high activity towards this reaction [35].The polymer incorporatingsterically confined NHCs ligands also shows high activity for the synthesis of carbonates [36].The porphyrin based porous organic polymer like M(Por)OP [37] and M/POP-TPP [38]shows excellent activity for cyclic carbonates. The porous organic polymer (POP) containing metal salen

Fig. 8. (a) Structure of tannic acid [31]and (b) reaction mechanism for the synthesis of cyclic carbonates catalysed by pyridine alcohol [30].


7

Fig. 9. Synthetic pathway of (a) azo-linked frameworks (PAFs) and (b) o-hydroxyazo-hierarchical porous organic polymers (HAzo-POPs).

complexes [39,40]shows high reactivity as well as excellent recyclability. Recently, we applied the catechol porphyrin (2,3-DhaTPh and 2,3-DmaTph)based covalent organic frameworks (COF) as an organocatalysts for the synthesis of carbonates andoxazolidinones (Fig. 11) [41]. With high functionalities on GO the amine functionalized GO (AP-GO) shows high reactivity towards the carbonates at the atmospheric pressure (Fig. 12) [42].The Yuan et al. utilized graphitic carbon nitride containing the rich amount of the hydroxyl as well as amine functional group, the high surface area and acid base nature are responsible for the synthesis of carbonates [42b].The Lewis acidic nature of metal based porous material also help to catalyse the cycloaddition reaction such as Zn-SBA-15/KI [43],titanate nanotubes (TNT) [44],peroxoniobate salts and organic bases [45], and silica grafted niobium pentachloride [46].Song et al. utilized C60fullerenol as HBD catalysts, the presence

of hydroxyl functional group on fullerenol helps to catalyse reaction effectively [47].Sun et al. synthesized a bifunctional Zn/SBA-15 supported ammonium salt (NH3IeZn/SBA-15) as singlecomponent heterogeneous catalyst for this reaction [48].Very recently, same group synthesized periodic mesoporousorganosilica with urea and pyridine functional groups lining the pore structure (PMO-UDF) for this reaction in which pyridine molecule activates the carbon dioxide and urea acts as a HBD catalysts for activation of epoxide [49]. Fig. 7. We have compared all the heterogeneous catalysts in four parts i. e. MOFs, ILs, organocatalysts and other porous materials. From the point of view of turn over frequency (TOF) below we compared some selected catalysts which shows high activity towards the cycloaddtion reaction which provides the high TOF (Table 3). The stability of any heterogeneous catalysts are the important factor,

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Fig. 10. (a) Structure of polymer containing sterically confined NHCs ligands and (b) reaction mechanism of cycloaddition reaction catalysed by fullerenol.

Fig. 11. Structures of 2,3-DhaTph and 2,3-DmaTph COF utilized as catalysts for the synthesis of cyclic carbonates.

stable the catalysts avoids the contamination of products by the degradation of catalyst the stability of active catalysts also compared. Among the all heterogeneous catalysts the metal containing material and polymers having provided the high TOF than the organocatalysts. Figs. 8e10.

6. Conclusions Among the various fantastic products derived from the CO2, cyclic carbonates are intensively studied by using homogeneous as well as heterogeneous catalytic system. In this account we have


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Fig. 12. Synthetic pathway for the synthesis of AP-GO catalyst.

Table 3 Comparision of TOF and thermal stability of all mentioned catalysts. Entry

Catalyst

Thermal stability of catalyst( C)

TOF (h1)

Reference

1 2 3 4 5 6 7 8 9 10

MOF Ni-TCPE1 IL [(CH2CH2OH)Bim]ZnBr3 TBB-Bpy@Salen-Co Tannic Acid Zn(OPO)2 HAzo-POPs [(Por)OP] Co/POP-TPP 2,3-DhaTph Zn/SBA-15

275 e 280 210 e 200 300 350 300 300

1000 794 82.66 200 22,000 2570 3183 436 980 306

[10] [23] [19a] [31] [33] [35] [37] [38] [41] [47]

summarized the recent development of heterogeneous catalytic systems including MOFs, ILs, organocatalysts and porous materials for the synthesis of cyclic carbonates. Due to the highly porous as well as crystalline nature of MOFs and other porous are extensively studied material for this reaction some are showing very mild reaction conditions. The task specific ILs with various functionality including polymer are also well established and shows higher recycle run as compared to other material. The nature of heterogeneous catalysts (crystalline and porous), functionalities of catalysts (acid-base) and activity of catalyst is important tasks for this

reaction. In future for this reaction, various methodology based active heterogeneous catalyst will arises with very mild conditions and will be expected at large scale. Acknowledgements Prof. BMB acknowledges editor for kind invitation and VBS acknowledges Dr.PradipPachfule to kind support and University Grant Commission (UGC), India for providing Senior Research Fellowship (SRF).

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