PNNL

Abstract

Metal–organic frameworks (MOFs) heterostructures exhibit unique properties beyond those of individual components, but their design requires an understanding of energetic and kinetic controls at MOFs–substrate interfaces. Although structure relationship has been widely applied in heterostructure design, it overlooks the interplay between organic ligand and substrate which defines the kinetics and energetics in the final structure. Herein we used zeolitic imidazolate frameworks (ZIF-8) on ZnO as a model system to evaluate this interplay via in situ monitoring and simulations. Our results show that selective 2-methyl-imidazole (2-MIM) ligand binding to ZnO surface steps modulates ZnO dissolution kinetics hence Zn2+ release rate, tuning local supersaturations that dictate ZIF-8 crystallization kinetics. The critical thickness for transition from 2D to 3D growth is dictated by competition between interfacial and strain energies. The atomic-scale mechanism of the coupled substrate dissolution and MOF growth, mediated by selective linker-substrate binding, furnishes a new synthesis pathway for other complex heterostructures.