Chemospecific Heterostructure and Heteromaterial Assembly of Metal-Organic Framework Nanoparticles.

Nanoparticles of highly porous metal-organic frameworks (MOFs) are some of the most exciting nanomaterials under development, with potential applications that range from biomedicine and catalysis to adsorption technologies. However, our synthetic methodologies to functionalize and manipulate MOF nanoparticles (NPs) are less well developed than they might be. Here we create MOF NPs derivatized with hydrazone units on their exterior, enabling chemospecific reversible dynamic covalent modification of structures on the external surface. Pairwise combinations of nanometer-sized building blocks with complementary dynamic covalent surface units can be used to prepare heterostructure assemblies (i.e., two MOFs with different structures and morphologies) and heteromaterial assemblies (a MOF with a nanoparticle of another kind, in this case gold) in which the directional molecular-level dynamic covalent links demand intimate mixing of the two nanoscale components. Crucially, the defining characteristic of the MOF components─their porosity─is minimally affected by the external functionalization and interparticle linking. The development of atomically precise dynamic covalent functionalization on the external surface of MOF NPs opens up new avenues for programmable frameworks with responsive behaviors and modular assembly of porous materials with precise control over the spatial organization of multiple nanoscale building blocks.