Individually Encapsulated Frame-in-Frame Structure

A platinum-based nanoframe is a hollow frame with superior catalytic behavior, and a metal-organic framework (MOF) is another porous frame with multifunctionalities. Here, we present the combination of these two components into an individually encapsulated frame-in-frame structure. Via the surface functionalization with hexadecyltrimethylammonium bromide (CTAB) as the bridging layer, the Pt-Ni nanoframe is encased in a special MOF, zeolitic imidazolate framework-8 (ZIF-8), to achieve a single core-shell structure, as evidenced by the three-dimensional tomography. The growth trajectory of such frame-in-frame nanocomposite is also tracked, revealing that ZIF-8 first nucleates in the solution, then attaches to the surface of the nanoframe, and finally grows to capture the entire nanoframe, accomplishing the one-in-one encapsulation. Following the same concept, by utilizing ZIF-67 as the sacrificial layer, the Pt-Ni nanoframe is further solely embedded in ZIF-8 to form the single yolk-shell structure, which has a cavity between the core and the shell. This work provides a new method to build frame-in-frame structures, consisting of different frameworks, and to explore their synergistic properties.