Synergistic effect of π-π and p-π conjugation of a commercial amine for enhanced photocatalytic CO2 cycloaddition reaction

Abstract

Designing a low-cost and efficient photocatalytic system to produce high-valuable carbonates from the cycloaddition of CO₂ by using clean and renewable sunlight as the driving force shows great research potential. Here, a commercially available 4,4''-diamino-p-terphenyl (DT) was directly employed to promote the photocatalytic cycloaddition of CO₂ and various epoxides under visible light irradiation. As high as 95 % yield of target carbonate was obtained using blue LED (>450 nm) as a light source for 6 h under solvent-free/atmospheric CO₂/room temperature conditions. Even under irradiation of natural light, a good yield of 68 % carbonate can also be achieved under ambient conditions. Moreover, in situ EPR and a series of controlled experiments were conducted to investigate the plausible photocatalytic mechanism, demonstrating that amino-containing DT with both π-π and p-π conjugated structure provides abundant basic sites and photogenerated electrons/holes as active sites for CO₂ activation and ring opening of epoxides at the same time.