Photocatalyzed Reduction of Chromium(VI) and Thermal-Driven Heterogeneous Separation

We use an ionic self-assembly to build supramolecular catalysts using polyoxometalates (POM) and a common commercial surfactant with oppositely charged hexadecyltrimethylammonium bromide (CTAB). The supramolecular catalysts can dissolve in ionic liquid but become immiscible in water. On the basis of these properties, a new-style catalytic system was constructed by supramolecular catalysts and temperature-sensitive ionic liquid, tetrabutylphosphonium trifluoroacetate ([P4444][CF3COO]), in water. [P4444][CF3COO] aqueous solution can form a microemulsion at 298 K, and supramolecular catalysts can exist in the microemulsion phase. Phase separation occurs when the temperature is increased. So, the catalysts can be separated via the change in temperature. Moreover, supramolecular catalysts in ionic liquid can avoid poisoning in the catalytic process. This new-style catalytic system could be of great significance for cost savings in industry.