[HDBU]Br@P-DD as Porous Organic Polymer-Supported Ionic Liquid Catalysts for Chemical Fixation of CO₂ into Cyclic Carbonates

Abstract

The chemical fixation of CO2 into high value-added cyclic carbonates is of significant potential and sustainability to address the energy and ecological issues. [HDBU]Br@P-DD-m/n, a series of porous organic polymer-supported ionic liquids (PSILs), were fabricated in this work through a one-pot four-component reaction of DMAEMA, DVB, 4-bromobutyric acid, and DBU. The formation of [HDBU]Br and construction of the P-DD polymer network proceeded concurrently with the support of the in situ-formed IL being achieved simultaneously. Characterization of the PSILs by IR, ICP, BET, SEM, and TGA etc. showed that the as-prepared catalysts possessed versatile hierarchical porosity with varying ionic densities and excellent thermostability. The porosity of the copolymer skeleton was found to be affected by the accompanying formation of [HDBU]Br. The PSILs were then evaluated as catalysts for the cycloaddition reaction of CO2 with epoxides, among which [HDBU]Br@P-DD-4/1 showed the optimal performance under atmospheric pressure and solvent-/cocatalyst-free conditions (95% yield and 99% selectivity for CO2 cycloaddition with epichlorohydrin). By correlating the performance and structures of the catalysts, the synergistic effect of the tertiary amine, [HDBU]Br, and pore distribution was demonstrated. In addition, the catalyst was found to be applicable in synthesizing a range of differently substituted carbonates in good to excellent yields. Finally, the catalyst could be recovered readily and good catalytic activity was still observed after use for 6 runs. The work not only provided an active, reusable, and metal-free heterogeneous catalyst for the fixation of CO2 into cyclic carbonates but also developed a facile one-step multicomponent strategy for constructing PSIL catalysts, which would be promising to find wide applications in catalysis and organic synthesis field.

Co(II)–N4 Catalysts for the Coupling of CO2 with Epoxides into Cyclic Carbonates: Catalytic Activity, Computational and Kinetic Studies

“…In terms of the activation mode for this transformation, the common feature for a catalytic system involves the activation of epoxide with a Lewis acid center followed by a nucleophilic attack, subsequent ring opening of epoxide and insertion of CO 2 to form the desired cyclic carbonates . To date, various kinds of catalysts, such as organocatalysts − (e.g., quaternary ammonium salts, ionic liquids, and organoboron catalysts) and metal complexes , (e.g., salen–metal complexes, metalloporphyrins and their analogues), have been developed to mediate the formation of cyclic carbonates. Most successful examples of binary/bifunctional catalytic systems consist of two active centers in which metal complex serves as Lewis acid metal center in combination with cocatalyst as a nucleophilic site (often quaternary ammonium with a halogen anion, such as tetrabutyl ammonium bromide, TBAB) for the epoxide ring-opening step. , …”

Superlative Porous Organic Polymers for Photochemical and Electrochemical CO2 Reduction Applications: From Synthesis to Functionality

“…POPs have been envisaged as a strong contender for CO 2 RR applicability on account of its excellent structural and compositional tailoring, higher stability, versatile polymerization, and perennial porosity, which are the primary parameters that govern the catalytic application of any material. − In order to augment the CO 2 RR activity of POP-based materials, heteroatom-abundant microporous frameworks and surface functionalization have been utilized. However, recently, researcher interest has been inclined toward pore tailoring, which has given rise to state-of-the-art POP materials rich in surface-active sites responsible for catalysis .…”

Multifunctional Zn-N4 Catalysts for the Coupling of CO2 with Epoxides into Cyclic Carbonates

“…However, this reaction cannot take place spontaneously, and suitable catalysts are generally required for the efficient conversion of CO 2 . Over the past decades, various catalysts have been successfully developed to catalyze the cycloaddition reaction, including organocatalysts (e.g., quaternary ammonium salts, ionic liquids, and organoboron catalysts), ,− metal complexes catalysts (e.g., salen–metal complexes and metalloporphyrin-based complexes), ,− and heterogeneous catalysts (e.g., porous organic polymers and metal organic frameworks). − Typically, these active catalytic systems involve a Lewis acidic metal center for the activation of the C–O bond of the epoxide and a nucleophilic site (such as halogen anion, Br – or I – ) for the epoxide ring-opening step . Thus, a simple nucleophilic reagent such as tetrabutyl ammonium bromide (TBAB) is widely used in binary catalytic systems together with metal complexes.…”