Three-dimensional van der Waals open frameworks

Abstract

Open-framework materials are constructed by connecting molecular components via strong bonds. It is generally believed that non-covalent interactions are too weak to hold the building blocks and generate stable open voids. Here we show that van der Waals interactions enable the construction of robust three-dimensional frameworks, referred to as van der Waals open frameworks (WaaFs). The key to successful synthesis of WaaFs is the use of octahedral metal–organic polyhedra with size larger than 2 nm as building blocks and their packing into a sparse diamond network with large extrinsic porosity. The well-defined faces composed of multiple planar moieties increase the intermolecular contact area to achieve an interaction energy above 400 kJ mol−1. We show that the WaaFs exhibit high thermal stability and high specific surface area as well as framework assembly with a reversible nature. In reticular chemistry, the formation of strong chemical bonds between molecular components is typically considered a core prerequisite for synthesizing open-framework materials. Now a series of robust frameworks have been assembled through van der Waals interactions; the stacking of polyhedral molecular building blocks results in the formation of three-dimensional open diamond networks.