Tetra-1,3-Diketone Resorcinarene Ion Pair as Metal- and Halide-Free Organocatalyst for Carbon Dioxide Fixation Under Atmospheric Pressure

Abstract

The development of efficient and environmentally friendly catalysts for CO2 cycloaddition remains a significant challenge due to the corrosion, pollution, and purity issues caused by conventional halide-containing systems. Herein, we present a halide-free tetra-1,3-diketone resorcinarene ion pair catalyst that facilitates CO2 fixation under mild conditions (120 °C, 0.1 MPa) through a dual activation mechanism—CO2 activation by the resorcinarene carbanion and epoxide activation via H-bonding. This catalytic system has been shown to achieve high conversion (83–99%) for terminal epoxides, retain notable activity for internal epoxides, and demonstrate exceptional thermal stability (> 230 °C) and recyclability (four cycles without significant loss of activity). This system offers a sustainable alternative to traditional halide catalysts, combining environmental advantages with practical industrial feasibility.

Keywords: carbon dioxide, epoxide, halide-free, ion pair, resorcinarene