Polyoxometalate-based phase transfer catalysis for liquid–solid organic reactions: a review
Phase transfer catalysis combines the advantages of homogeneous and heterogeneous catalysts and therefore attracts ever-growing interest for environmentally-friendly sustainable processes. Polyoxometalates (POMs) are a class of molecular metal oxides showing numerous applications in various catalytic processes due to their unique acid/base and redox features. The tunable molecular structures of POM anions and countercations bring about facile adjusting of POMs' physical and chemical properties including solubility, through which many POM-based phase transfer catalysts are fabricated, such as reaction-controlled, temperature-responsive and photo-sensitive phase transfer catalysts. This mini-review summarizes the recent progress in POM-based phase transfer catalysis for liquid–solid organic reactions.