Synthesis of Cyclic Carbonate Catalyzed by DBU Derived Basic Ionic Liquids

POPs to COFs by post-modification: CO2 chemisorption and dissolution

Porous organic polymers (POPs) and covalent organic frameworks (COFs) are hierarchical nano materials with variable applications. To our knowledge, this is the first report of a post-modified, non-renewable, DMSO-soluble M-POP/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) upon atmospheric H2O/CO2 trapping after 48 h, forming a DBUH+·HCO3- adduct, as verified by solution carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. The success of the post-modification resulting from aldehyde enriched POPs was proven spectroscopically. The accessible functional group was reacted with excess monoethanolamine (MEA) resulting in the formation of M-POP. Away from CO2 physisorption, only few examples have been reported on the chemisorption process. One such example is the ethylene diamine-functionalized E-COF, capable of capturing CO2via carbamation. This was evidenced by several qualitative measurements including colorimetry and conductivity, which showed an unprecedented water solubility for a 2D COF material. The crystallinity of COFs as a result of post-modification was proven by powder X-ray diffraction (PXRD).

Efficiency in Carbon Dioxide Fixation into Cyclic Carbonates: Operating Bifunctional Polyhydroxylated Pyridinium Organocatalysts in Segmented Flow Conditions

Novel polyhydroxylated ammonium, imidazolium, and pyridinium salt organocatalysts were prepared through N-alkylation sequences using glycidol as the key precursor. The most active pyridinium iodide catalyst effectively promoted the carbonation of a set of terminal epoxides (80 to >95% yields) at a low catalyst loading (5 mol%), ambient pressure of CO₂, and moderate temperature (75 °C) in batch operations, also demonstrating high recyclability and simple downstream separation from the reaction mixture. Moving from batch to segmented flow conditions with the operation of thermostated (75 °C) and pressurized (8.5 atm) home-made reactors significantly reduced the process time (from hours to seconds), increasing the process productivity up to 20.1 mmol_(product) h^-1 mmol_(cat)^-1, a value ~17 times higher than that in batch mode.

Metal phosphonates as heterogeneous catalysts for highly efficient chemical fixation of CO2 under mild conditions

Two new compounds with novel structures were prepared, one of which displays excellent catalytic activity to transform CO2 gas to cyclic carbonates under mild conditions and free of solvent.

CO2 fixation into cyclic carbonates catalyzed by single-site aprotic organocatalysts

The catalytic activity of a series of onium salts for the synthesis of cyclic carbonates have been investigated experimentally and theoretically.

Hydrogen bond donor functionalized poly(ionic liquid)s for efficient synergistic conversion of CO2 to cyclic carbonates

The development of metal-free, high effective and recyclable catalysts plays a pivotal role in transforming CO2 into high value-added products such as cyclic carbonates. In this paper, we introduced the hydrogen bond donor (HBD) groups into poly(ionic liquid)s via free radical polymerization, which successfully combined the HBD and ionic liquids (ILs) into one heterogeneous catalyst. The HBD could synergistically activate epoxides with hydroxyl functionalized ionic liquids and efficiently catalyze the cycloaddition of CO2 into cyclic carbonates. The yield of propylene carbonate (PC) reached 94% (at 105 °C, 2 MPa CO2, 3 h), which far exceeded poly(ionic liquid)s without HBDs functionalization (PC yield 72%), and even approached bulk ionic liquids (PC yield 95%). Moreover, HBD-functionalized poly(ionic liquid)s (HPILs) exhibited excellent recyclability after five runs and afforded wide substrate scope. According to the experimental results, 1H NMR spectra and density functional theory (DFT) calculations showed 2-hydroxyethyl methacrylate (HEMA) and the hydroxyl of ILs would form strong H-bonds with epoxides contributing to the ring-opening process of epoxides, and a possible HBD and nucleophilic anion synergistically catalytic mechanism was proposed. The method herein paved a brand new way for green technology and utilization of poly(ionic liquid)s.

Synergetic activation of CO2 by the DBU-organocatalyst and amine substrates towards stable carbamate salts for synthesis of oxazolidinones

The development of an efficient methodology to transform CO2 into valuable chemicals has attracted increasing attention concerning the challenging issues of CO2-utitlization.

Poly(hydroxyurethane): catalytic applicability for the cyclic carbonate synthesis from epoxides and CO2

We have developed a synthetic methodology using poly(hydroxyurethane) as an organocatalyst for the chemical fixation of CO2 into epoxides, leading to the formation of five-membered cyclic carbonates with remarkably high selectivity and yields. The catalyzed reaction was applicable to various epoxides.

Theoretical study on the absorption of carbon dioxide by DBU-based ionic liquids

In this article, 20 ns molecular dynamic (MD) simulations and density functional theory (DFT) were used to investigate the absorption of CO2 molecules by some functionalized 1,8-diazabicyclo[5,4,0]-udec-7-ene (DBU)-based ILs. According to the MD results, the highest coordination number for NC is observed in the case of [DBUH+][Im-], which indicates that the functionalization of the imidazole anion by different alkyl groups decreases the interaction ability of the anion with CO2 molecules. The addition of water molecules to the ILs decreases the ability of the anion to interact with CO2 because of the hydrogen bond formation between the imidazole anions and water. Two different paths were proposed for CO2 absorption by the ILs, and the effect of alkyl groups on the kinetics and thermodynamics of the reaction was analyzed by using the M06-2X functional at the 6-311++G(d,p) level of theory in the gas phase and water. On the basis of the results, CO2 absorption is more favorable in [DBUH+][Im-], thermodynamically. Kinetic parameters show that the alkylation of the imidazole anion by ethyl, propyl, iso-propyl, and phenyl groups decreases the rate of CO2 absorption, because of the steric and electron-withdrawing effect of different alkyl groups. In the presence of water molecules, the lowest activation Gibbs energy is related to [DBUH+][Im-], which confirms the greater ability of this IL in CO2 absorption.