Organocatalytic Polymers from Affordable and Readily Available Building Blocks for the Cycloaddition of CO₂ to Epoxides

Abstract

The catalytic cycloaddition of CO2 to epoxides to afford cyclic carbonates as useful monomers, intermediates, solvents, and additives is a continuously growing field of investigation as a way to carry out the atom-economic conversion of CO2 to value-added products. Metal-free organocatalytic compounds are attractive systems among various catalysts for such transformations because they are inexpensive, nontoxic, and readily available. Herein, we highlight and discuss key advances in the development of polymer-based organocatalytic materials that match these requirements of affordability and availability by considering their synthetic routes, the monomers, and the supports employed. The discussion is organized according to the number (monofunctional versus bifunctional materials) and type of catalytically active moieties, including both halide-based and halide-free systems. Two general synthetic approaches are identified based on the postsynthetic functionalization of polymeric supports or the copolymerization of monomers bearing catalytically active moieties. After a review of the material syntheses and catalytic activities, the chemical and structural features affecting catalytic performance are discussed. Based on such analysis, some strategies for the future design of affordable and readily available polymer-based organocatalysts with enhanced catalytic activity under mild conditions are considered.

Polyhydroxyurethanes from Biobased Monomers and CO2: A Bridge between Sustainable Chemistry and CO2 Utilization†

“…[ 78,95 ] Moreover, while still facing significant limitations in terms of low molecular masses and polymerization yields, [ 96‐98 ] PHUs and hybrid PHU‐based materials, [ 97 ] are being increasingly regarded as potential, isocyanate‐free (hence the term NIPUs, non‐isocyanate polyurethanes) alternatives to traditional, isocyanate‐based polyurethanes (PUs), which is a desirable target in terms of sustainability and health safety. [ 99 ] On top of this, recent advances [ 34‐35,100‐101 ] in homogeneous [ 102‐107 ] and heterogeneous [ 108‐113 ] catalysis have greatly improved the accessibility of terminal 5CCs that can be obtained even by recycling impure waste CO 2 from industrial emissions, [ 114‐116 ] while efficient catalyst for the synthesis of other crucial internal 5CCs for PHUs preparation such as carbonated fatty acid esters and carbonated vegetable oils is currently under development. [ 117‐123 ] Therefore, this review will focus on the main recent advances on the preparation of PHUs using CO 2 and biobased epoxides as the starting materials.…”

Samarium- and Ytterbium-Grafted Periodic Mesoporous Silica for Carbon Dioxide Capture and Conversion

“…21−27 Among the various classes of heterogeneous 28,29 or reusable 30,31 catalytic systems for the cycloaddition of CO 2 to epoxides, surface-grafted Lewis acidic metal complexes display readily available, convenient catalytic components for the synthesis of cyclic carbonates. 12,14,32,33 Compared to other metal-based heterogeneous systems such as tethered metalorganic complexes, 34 metalorganic frameworks, 35 and covalent organic polymers, 36,37 surface-grafted complexes do not involve sophisticated and expensive networks of organic ligands to harness and immobilize the metal center. The latter framework materials often require the use of expensive building blocks 38 and noble-metal catalysis 39 as well as multiday, 40 multistep synthesis procedures.…”

“…The generation of highly dispersed and well-defined single metal sites on inert supports has recently emerged as a valuable strategy to fabricate highly active catalytic systems, optimize the utilization of expensive or rare metals, and exploit mechanistic pathways not available for larger assemblies of atoms. – In this context, surface organometallic chemistry (SOMC), – based on the grafting of organometallics onto a dehydroxylated metal oxide surface, offers a prime route toward site-isolated metal complexes, , with ligands tailor-made for the targeted catalytic process . In this vein, SOMC afforded highly active immobilized Lewis acids for the cycloaddition of CO 2 to epoxides, – providing a privileged nonreductive strategy – to convert CO 2 – into value-added cyclic organic carbonates. – Among the various classes of heterogeneous , or reusable , catalytic systems for the cycloaddition of CO 2 to epoxides, surface-grafted Lewis acidic metal complexes display readily available, convenient catalytic components for the synthesis of cyclic carbonates. ,,, Compared to other metal-based heterogeneous systems such as tethered metalorganic complexes, metalorganic frameworks, and covalent organic polymers, , surface-grafted complexes do not involve sophisticated and expensive networks of organic ligands to harness and immobilize the metal center. The latter framework materials often require the use of expensive building blocks and noble-metal catalysis as well as multiday, multistep synthesis procedures .…”

Polyhydroxy Ionic Polymer Catalysts for Highly Selective Cycloaddition of Carbon Dioxide and Epoxides

“…And they can be easily separated from reaction system with high activity and stability. Zhang and co‐workers [8f] prepared a hydroxyl functional ionic liquid copolymer P + Br − (CH 3 )OH‐HCP for the CO 2 coupling with glycidyl methacrylate, which gave >99 % conversion and 99 % selectivity at 80 °C under 1.0 MPa and 24 h. Recently, ternary copolymerized PILs were also synthesized and used to convert CO 2 into cyclic carbonates [9] . In this respect, the exploration of heterogeneous catalysts with simple ionic liquid moiety, high catalytic activity and good recycling performance is an important route to decrease the operation cost and achieve the industrialization process.…”