Cobalt phthalocyanine-based nanodots as efficient catalysts for chemical conversion of CO2 under ambient conditions

The chemical fixation of CO2 into epoxides to afford cyclic carbonates has received considerable attention due to the 100% atom economy, which is in accordance with the concept of green chemistry and sustainable development. Here, we develop a facile and high-output strategy to fabricate cobalt phthalocyanine-based nanodots (CoPc-NDs) by the carbonization of citric acid and cobalt phthalocyanine complex. Due to the high thermal stability of phthalocyanine, the macrocycle is well preserved in the core of nanodots under the controlled hydrothermal temperature. The as-prepared CoPc-NDs disperse well in water with a nanoscale size about 70 nm. The morphology and chemical composition of CoPc-NDs are characterized by transmission electron microscopy, dynamic laser scattering, X-ray powder diffraction, X-ray energy spectrum, and absorption spectrum. Compared with the organometallic complex, such as cobalt tetra-nitrophthalocyanine and cobalt tetra-aminophthalocyanine, CoPc-NDs show better catalytic performance for the conversion of epoxides into carbonates. The kinetic experiments of three catalysts are investigated and compared under the same conditions using styrene oxide as substrate. Finally, a tentative mechanism for the catalysis was proposed and described.