A single Au nanoparticle anchored inside the porous shell of periodic mesoporous organosilica hollow spheres

An ideal metal catalyst requires easy contact with reaction reagents, a large number of exposed active sites, and high stability against leaching or particle agglomeration. Anchoring a metal core inside a porous shell, though scarcely reported, may combine these advantages owing to the integration of the conventional supported metal arrangement into a core@void@shell architecture. However, achieving this is extremely difficult owing to the weak core-shell affinity. Herein, we report, for the first time, an approach to overcome this challenge by increasing the core-shell interaction. In this regard, we synthesized a novel Au@void@periodic mesoporous organosilica (PMO) architecture in which a single Au core is firmly anchored inside the porous shell of the hollow PMO sphere. The non-covalent interactions between the poly(vinylpyrrolidone) (PVP) groups of functionalized Au and ethane moieties of PMO facilitate the movement of the Au core towards the porous shell during the selective alkaline etching of Au@SiO2@PMO. Shell-anchored Au cores are superior to the suspended cores in the conventional Au@void@PMO in terms of contact with reagents and exposure of active sites, and hence show higher catalytic efficiency for 4-nitrophenol reduction. The methodology demonstrated here provides a new insight for the fabrication of versatile multifunctional nanostructures with cores anchored inside hollow shells.