Transferring Porosity Across Physical States Using Metal–Organic Cages: Porous Liquids, Glasses, Rubbers, and More

The development of porous materials that retain tailored porosity across different physical states beyond crystalline solids (e.g., liquid or glassy) could yield new functional materials for diverse applications, yet it remains challenging. To address this, researchers have turned to discrete porous cages such as metal-organic cages (MOCs) and metal-organic polyhedra (MOPs). The organization and physical state of these materials are governed by inter-cage interactions that can be modulated without altering the intrinsic porosity of the individual cages. In this minireview, we highlight how the peripheral functionality of such cages governs their interactions and physical state and explain how it can be harnessed to preserve and transfer porosity across distinct physical states, including liquids, glasses, and rubbers. We conclude by outlining emerging properties and potential applications for the resultant unique porous states.