Infinite building blocks for directed self-assembly of a supramolecular polyoxometalate-cyclodextrin framework for multifunctional oxidative catalysis

The utility of infinite building blocks (IBBs) has encouraged the facile construction of porous organic-inorganic hybrid materials such as metal-organic frameworks. However, this strategy remains less explored for building functional supramolecular frameworks that are assembled by weak supramolecular interactions. Here, we report the self-assembly of a supramolecular polyoxometalate-cyclodextrin (POM-CD) framework directed by IBBs of ({MnV12Ce6}{PW10V2}(2))(infinity) for multifunctional oxidative catalysis. The IBBs exhibit an infinite 1D rod shape embedded by {MnV12} and {PW10V2} POM clusters which specifically interact with the outer walls of alpha-CD because of a weak chaotropic effect and size-mismatch. This has allowed the ordered packing of alpha-CD between adjacent IBBs via hydrogen bonding and van der Waals contacts, leading to a porous framework containing interconnected channels along two dimensions, with the largest opening up to 12 x 17 angstrom. The incorporation of catalytically active POM clusters on the porous channels enables the high performance of the POM-CD framework towards selective oxidation of sulfides to sulfoxides. Moreover, cross-linking the POM-CD framework with hexamethylene diisocyanate afforded a more stable porous framework that can be used as an authentically heterogeneous catalyst for not only sulfoxidation but also oxidative cleavage of styrenes under harsher conditions. The robust cross-linked framework can preserve its structural integrity after cycling 5 times with little loss of catalytic performance. This work may pave the way for the rational design of porous organic-inorganic hybrid materials with customized functionalities based on the IBB strategy.