Imidazolium functionalized carbon nanotubes for the synthesis of cyclic carbonates: reducing the gap between homogeneous and heterogeneous catalysis

Abstract

Single walled carbon nanotubes were functionalized with imidazolium based salts and successfully used as catalysts for the conversion of CO2. The novel materials displayed excellent catalytic activity.

Modified Nanocarbons for Catalysis

“…The catalyst can be separated by centrifugation followed by washing with diethyl ether and could be reused 10 times with a significant decrease in the catalytic activity just in the 10 th cycle. Polymerization of a bis‐vinylimidazolium bromide 66 and a styryl imidazolium chloride 67 through a direct procedure involving self‐assembly of the imidazolium moieties followed by radical polymerization of vinyl groups, led to highly‐loaded SWCNT‐polyimidazolium salts hybrids (Scheme ) . Raman spectra confirmed the covalent linking of polymer chains onto the nanotube surface and the BET specific surface area values were 100 m 2 g −1 and 360 m 2 g −1 for 68 and 69 , respectively.…”

“…Polymerization of a bisvinylimidazolium bromide 66 and a styryl imidazolium chloride 67 through a direct procedure involving self-assembly of the imidazolium moieties followed by radical polymerization of vinyl groups, led to highly-loaded SWCNT-polyimidazolium salts hybrids (Scheme 23). [57] Raman spectra confirmed the covalent 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 linking of polymer chains onto the nanotube surface and the BET specific surface area values were 100 m 2 g À1 and 360 m 2 g À1 for 68 and 69, respectively. The hybrids were applied as catalysts in the conversion of carbon dioxide and some epoxides to the corresponding cyclic carbonates with TON of up to 1184 and TOF of 395 h À1 with no need for additional Lewis acid co-catalyst.…”

Bi-functional heterogeneous catalysts for carbon dioxide conversion: enhanced performances at low temperature

“…8 To achieve an easy recovery from the reaction mixture and reuse of the catalyst for multiple cycles, most of these salts were also heterogenized 9 on different supports. Silica-based porous materials, 10,11 polymers, 12,13 single as well as multi-walled carbon nanotubes, [14][15][16] and more recently carbon nanohorns 17 among others were already selected for this purpose. The mechanism of the reaction is well known and was already reported in various publications.…”

“…10,16 For comparison, the activity of the all-silica MCM-41 solid functionalized with imidazolium moiety (XS-MCM-41-Imi) was studied as well (see entry 1 in Table 2). Moreover, before starting the investigation in the presence of the bifunctional catalysts an additional catalytic test adding a small amount of ZnCl 2 (corresponding approximatively to the quantity inserted in the silica framework) to the reaction mixture was performed in order to evaluate the positive contribution of a salt with Lewis acid properties under homogeneous conditions.…”

Noncovalently functionalized carbon nanotubes immobilized Fe–Bi bimetallic oxides as a heterogeneous nanocatalyst for reduction of nitroaromatics

“…However, the hydrophobicity and self-coalesce of the CNTs sometimes restrict their application. Consequently, the chemists have dedicated to functionalize the CNTs with different kinds of organic molecules, such as 3, 4-dihydroxybenzaldehyde [43], pyridine [44], imidazolium [45], quinine [46], so that the CNTs are kept in the dispersed status, the covalent and non-covalent functionalization strategies have been well developed. [47,48] However, grafting many hydrophilic groups with covalent bond on the CNTs may inevitably damage the CNT structures, while a non-covalent functionalization may preserve their good properties.…”