Synthesis of Isotypic Giant Polymolybdate Cages for Efficient Photocatalytic C-C Coupling Reactions

The construction of isotypic high-nuclearity inorganic cages with identical pristine parent structure and increasing nuclearity is highly important for molecular growth and structure-property relationship study, yet it still remains a great challenge. Here, we provide an in situ growth approach for successfully synthesizing a series of new giant hollow polymolybdate dodecahedral cages, Mo, Mo-I, and Mo-E, whose structures are growth based on giant polymolybdate cage Mo. Remarkably, they show two pathways of nuclear growth based on Mo, that is, the growth of 10 and 20 Mo centers on the inner and outer surfaces to afford Mo and Mo-I, respectively, and the growth of 10 Mo centers both on the inner and outer surfaces to give Mo-E. To the best of our knowledge, this is the first study to display the internal and external nuclear growth of a giant hollow polyoxometalate cage. More importantly, regular variations in structure and nuclearity confer these polymolybdate cages with different optical properties, oxidative activities, and hydrogen atom transfer effect, thus allowing them to exhibit moderate to excellent photocatalytic performance in oxidative cross-coupling reactions between different unactivated alkanes and N-heteroarenes. In particular, Mo and Mo-E with better comprehensive abilities can offer the desired coupling product with yield up to 92% within 1 h.