Facile Fabrication of Robust Supraparticles for Spatially Orthogonal Cascade Catalysis.

Macroscopically sized supraparticles (SPs) are emerging as cutting-edge materials for industrial applications because of their unique properties unachievable for their nano-building blocks, but their effective methods are lacking. Here, we develop a conceptually novel strategy to assemble binary or ternary nanoparticles (NPs) within compartments of droplets through electrostatic interactions, making it possible to facilely fabricate millimeter-sized multicomponent ionic supraparticles (ISPs). The assembled ISPs possess unexpectedly high mechanical strength (50 N per bead), being amenable to practical applications. The key factors governing the assembly behavior of nano-building blocks within water droplet compartments have been identified through regulating the size and charge density of NPs or ionic strength, providing key insights into multilevelled assembly of NPs beyond the conventional assembly. Our strategy is demonstrated to be versatile since a library of tailor-made ISPs containing multicomponent, diversely shaped and differently sized NPs can be facilely fabricated. As a proof of this concept, we showcase that this method enables to prepare spatially orthogonal cascade catalysts by co-assembling acidic, basic and metal sites in a single millimeter-scaled particles. The catalysts exhibited significantly enhanced catalytic efficiency in a one-pot cascade synthesis of α-alkylated nitriles and high operational stability (200 h) in industrially preferred fixed-bed reactors.