Porous soft materials with liquid-glass-crystal interconvertibility based on metal-organic polyhedra

The capability of materials to interconvert between different phases provides more possibilities for controlling materials’ properties without additional chemical modification. The study of state-changing microporous materials just emerged and mainly involves the liquefication or amorphization of solid adsorbents into liquid or glass phases by adding non-porous components or sacrificing their porosity. The material featuring reversible phases with maintained porosity is, however, yet to be achieved. Here, we synthesize metal-organic polyhedra (MOPs) that interconvert between the liquid-glass-crystal phases. The modular synthetic approach is applied to integrate the core MOP cavity that provides permanent microporosity with tethered polymers that dictate the phase transition. We showcase the processibility of this material by fabricating a gas separation membrane featuring tunable permeability and selectivity by switching the state. The liquid MOP membrane particularly shows a unique selectivity of CO2 over H2 with enhanced permeability, compared to most conventional porous membranes.