Clickable Norbornene-Based Zirconium Carboxylate Polyhedra

A common way to modify the properties of metal–organic polyhedra (MOPs) is to install pendant functionalities on the organic bridging ligands. These groups can then participate in coupling reactions to further decorate a given architecture. Via exploitation of click chemistry, it is possible to access a diverse library of MOPs that share a common core, which can reduce both synthetic complexity and cost. Herein, we report the formation of a reactive norbornene-based MOP through a one-pot tandem coordination-driven self-assembly/Diels–Alder reaction between fumaric acid and zirconocene dichloride (Cp2ZrCl2). The generality of this tandem process was illustrated by the subsequent synthesis of a norbornene-based Zr cluster formed from maleic acid and Cp2ZrCl2. We demonstrate post-assembly modification of this cage using versatile thiol–ene click chemistry, resulting in the formation of either individual functionalized MOPs or cross-linked polymer/MOP hybrid composites. The physical properties of these composites can be controlled by the addition of poly(ethylene glycol) diacrylate as a co-monomer, allowing for the synthesis of free-standing, flexible films at MOP loadings of 30–60% (w/w). These results demonstrate the effectiveness of thiol–ene click chemistry as a method of MOP functionalization, expanding the toolbox for the synthesis of new advanced materials.