N-Heterocyclic carbene functionalized MCM-41 as an efficient catalyst for chemical fixation of carbon dioxide

Sustainable conversion of carbon dioxide: the advent of organocatalysis

“…At a later stage, the same group has shown that a NHC-CO 2 adduct could also be immobilized on a MCM-41 support and the catalytic activity of this hybrid material in the coupling between CO 2 and epoxides was investigated. 64 Although applicable, these protocols based on NHC catalysts and their corresponding derivatives require high CO 2 pressures (> 20 bar) and temperatures (> 100 o C). The hybrid silica material is indeed recyclable; however, its multi-step synthesis and isolation may result in extra energy and cost consumption, compromising to some extend the overall process sustainability.…”

“…When NHC scaffolds (Scheme 3; R 1 = i-Pr, R 2 = H) were grafted onto a silica MCM-41 support, the resultant catalyst was active towards cyclic carbonate formation at 0.5 mol % catalyst loading under relatively mild conditions (T = 120 ºC, p(CO 2 ) = 20 bar, t = 24−48 h), whereas this supported catalyst was also used for the synthesis of oxazolidinones under even milder conditions (T = 80-100 ºC) affording N-substituted oxazolidinones in excellent yields. 64 A different NHC (R 1 = 2,6(i-Pr) 2 C 6 H 5 ; R 2 = H) was covalently embedded within a tubular, micro-porous organic network. When using this heterogeneous catalytic system, propylene oxide (PO) was quantitatively converted to propylene carbonate in 10 h with a catalyst load of only 0.065 mol % (Yield = 92%; TOF = 142 s -1 , T = 160 ºC, p(CO 2 ) = 30 bar).…”

Highly efficient conversion of CO2 at atmospheric pressure to cyclic carbonates with in situ-generated homogeneous catalysts from a copper-containing coordination polymer

“…Under the conditions of 1 atm CO 2 and 60°C, the epichlorohydrin substrate displays a good applicability for co-catalysts, that is, a high reactivity was obtained when coupled with most of the investigated co-catalysts (Table 2). In the previous studies [7,32], N-heterocyclic compounds were often applied to the conversion of CO 2 to cyclic carbonates due to the presence of nucleophilic sites. In our work, several N-heterocyclic compounds were also examined as possible co-catalyst, and an activity order was obtained with DMAP > IM > DBU > Py (entries 10-11, 13-14, Table 2), which is related to their nucleophilic and basic strength [23,33,34].…”

A heteropolyacid-based ionic liquid immobilized onto Fe3O4/SiO2/Salen/Mn as an environmentally friendly catalyst for synthesis of cyclic carbonate

“…In the past few decades, the numerous heterogeneous and homogeneous catalysts have been developed for the synthesis of cyclic carbonates from epoxides and CO 2 [30][31][32] -such as metal oxides [33], molecular sieves [34], ion-exchange resins [35], nanoparticles [36], alkali metal salts [37], quaternary ammonium salts [38][39][40], transition metal complexes [41][42][43][44], metal-organic frameworks [45], N-heterocyclic carbenes [46], Lewis acids or bases [47,48], ionic liquid [49][50][51][52][53], and so on. Among these catalysts, ionic liquids have been shown to have excellent activity in the synthesis of cyclic carbonates from carbon dioxide and epoxides.…”