Repetitive in situ recycling of degraded metal-organic frameworks within nanocapsules

We report the first example of repetitive in situ recycling of two metal-organic frameworks (MOFs), HKUST-1 and ZIF-8. By individually packaging MOF particles either in ultrathin polystyrene or mesoporous silica nanocapsules, the metal ions and the ligand molecules can be effectively confined within the capsules even after complete chemical degradation. Due to spatial compartmentalization, the homogeneity and local metal-ligand stoichiometry were well-kept throughout the sample. The degraded HKUST-1 can subsequently recrystallize back to its crystalline form within each polystyrene capsule through a simple vapor-assisted reconstruction step for at least five consecutive runs with 82% of the CO2 uptake capacity retained at the end while maintaining its original morphology. Mesoporous silica encapsulated ZIF-8, on the other hand, can undergo at least ten degradation-reconstruction cycles recovering 65% of its original N-2 uptake capacity.