Hollow\nMetal–Organic Framework Nanospheres\nvia Emulsion-Based Interfacial Synthesis and Their Application in\nSize-Selective Catalysis

Abstract

Metal–organic frameworks (MOFs)\nrepresent an emerging class\nof crystalline materials with well-defined pore structures and hold\ngreat potentials in a wide range of important applications. The functionality\nof MOFs can be further extended by integration with other functional\nmaterials, e.g., encapsulating metal nanoparticles, to form hybrid\nmaterials with novel properties. In spite of various synthetic approaches\nthat have been developed recently, a facile method to prepare hierarchical\nhollow MOF nanostructures still remains a challenge. Here we describe\na facile emulsion-based interfacial reaction method for the large-scale\nsynthesis of hollow zeolitic imidazolate framework 8 (ZIF-8) nanospheres\nwith controllable shell thickness. We further demonstrate that functional\nmetal nanoparticles such as Pd nanocubes can be encapsulated during\nthe emulsification process and used for heterogeneous catalysis. The\ninherently porous structure of ZIF-8 shells enables encapsulated catalysts\nto show size-selective hydrogenation reactions.