Impact of exposed crystal facets on oxygen reduction reaction activity in zeolitic imidazole frameworks

ZIF-67 is a representative type of metal-organic framework (MOF) developed for the oxygen reduction reaction (ORR) owing to its robust structure in alkaline electrolytes and the presence of the redox-active Co2+ species in the structure. In this work, the improvement of the ORR electrolytic performance of ZIF-67 in its pure phase by optimization of its crystal morphology and crystal facets has been presented. ZIF-67 nanocubes exhibit higher ORR activity than their bulk crystals. The enriched (100) facet in the nanocube crystals provides a higher number of exposed Co2+ sites resulting in improved ORR performances. Moreover, DFT study suggests a distinguished mechanism in the (100) facet highlighting the importance of crystal facets in electrochemical performances.

Metal-Organic Framework Aerogel for Full pH Range Operation and Trace Adsorption of Arsenic in Water

The UiO-66-NH₂ aerogel has been designed to remove As(III) and As(V) in the full pH range with a long lifetime. The efficiency of the aerogel for trace removal from river water samples at the sub-ppb level has been demonstrated. The feasibility for practical uses has been evaluated by breakthrough experiments operated at a liquid hourly space velocity (LHSV) of 38 h^-1 using a real water sample with a significant capacity of 284 mg g^-1. The UiO-66-NH₂ aerogel provides a lifetime of over 600 min, which is one of the highest lifetimes among the reported adsorbents for arsenic decontamination.