Scalable, Durable, and Recyclable Metal‐Free Catalysts for Highly Efficient Conversion of CO₂ to Cyclic Carbonates

Abstract

As eries of highly active organoboron catalysts for the coupling of CO 2 and epoxides with the advantages of scalable preparation, thermostability,a nd recyclability is reported. The metal-free catalysts show high reactivity towards aw ide scope of cyclic carbonates (14 examples) and can withstand ahigh temperature up to 150 8 8C. Compared with the current metal-free catalytic systems that use mol %c atalyst loading, the catalytic capacity of the catalyst described herein can be enhanced by three orders of magnitude (epoxide/cat. = 200 000/1, mole ratio) in the presence of ac ocatalyst. This feature greatly narrows the gap between metal-free catalysts and state-of-the-art metallic systems.A ni ntramolecular cooperative mechanism is proposed and certified on the basis of investigations on crystal structures,s tructure-performance relationships,k inetic studies,a nd key reaction intermediates. Scheme 1. The coupling reaction of CO 2 and epoxide.

Recent progress in the catalytic transformation of carbon dioxide into biosourced organic carbonates

“…97 On the other hand, the group of Wu reported a bifunctional organoboron organocatalyst able to achieve full conversion and excellent yield of GC at remarkably low (0.02 mol%) catalyst loading though under somewhat harsher reaction conditions (120°C, 20 MPa CO 2 ). 98 In the latter case, mechanistic studies indicated that the boron acts as a Lewis acid and activates the oxirane ring near a closely positioned ammonium iodide unit (Scheme 8). Lastly, Kleij et al showed that DBU can promote the formation of GC from Gly and other epoxy alcohols through the formation of a hemicarbonate intermediate under mild reaction conditions (45°C, 1 MPa CO 2 ).…”

A Novel Dopamine‐Based Boronate Esters with the Organic Base as Highly Efficient, Stable, and Green Catalysts for the Conversion of CO2 with Epoxides to Cyclic Carbonates

“…Finally, ring closure occurred by the alkyl carbonate attack on the terminal carbon atom to produce the corresponding cyclic carbonates and the boronate ester (B 4a ) catalyst. [ 5,18–20 ] After the release of ECH, the boronate ester (B 4a ) catalyst is regenerated and the catalysis continues in the same way.…”

“…However, to the best of our knowledge, until recently boron compounds are very rarely preferred as a potent class of organocatalysts for chemical fixation of CO 2 to highly demanding cyclic carbonates. [ 17–21 ] Therefore, we think that boronate esters as an efficient catalyst will remove some restrictions in the chemical fixation of CO 2 to valuable chemicals such as cyclic carbonate and polycarbonate.…”

Future prospects in boron chemistry: new boron compounds and Lewis acids for catalysis and materials science

“…Trivalent organoboron compounds are of increasing importance for capturing and reacting with small molecules [34,35] . The boron-mediated conversion of carbon dioxide to cyclic carbonates [36] and copolymers [Figure 2A] [37] and to formate [Figure 2B] [38,39] with bifunctional borylated catalysts is a rapidly evolving area of chemical catalysis oriented towards green chemistry.…”