Porous Capsules with a Large Number of Active Sites: Nucleation/Growth under Confined Conditions

This work deals with the generation of large numbers of active sites and with ensuing nucleation/ growth processes on the inside wall of the cavity of porous nanocapsules of the type (pentagon)12(linker)30≡{(MoVI)MoVI5}12{MoV2(ligand)}30. A first example refers to sulfur dioxide capture through displacement of acetate ligands, while the grafted sulfite ligands are able to trap {MoO3H}+ units thereby forming unusual {(O2SO)3MoO3H}5− assemblies. A second example relates to the generation of open coordination sites through release of carbon dioxide upon mild acidification of a carbonate‐type capsule. When the reaction is performed in the presence of heptamolybdate ions, MoO42− ions enter the cavity where they bind to the inside wall while forming new types of polyoxomolybdate architectures, thereby extending the molybdenum oxide skeleton of the capsule. Parallels can be drawn with Mo‐storage proteins and supported MoO3 catalysts, making the results relevant to molybdenum biochemistry and to catalysis. Stabilize it: The Keplerate is unique because of the existence of a large number of flexible and stepwise gateable crown ether type pores/channels and the practically endless possibilities of changing the interior due to the presence of numerous easily exchangeable internal ligands/functionalities; therefore it allows a nearly infinite number of internal reactions. Shown in the figure is the stabilization of the internal MoO3H+ between sulfite ligands.