A Single-Crystal Open-Capsule Metal–Organic Framework

Micro-/nanocapsules have received
substantial attention due to
various potential applications for storage, catalysis, and drug delivery.
However, their conventional enclosed non-/polycrystalline walls pose
huge obstacles for rapid loading and mass diffusion. Here, we present
a new single-crystal capsular-MOF with openings on the wall, which
is carefully designed at the molecular level and constructed from
a crystal-structure transformation. This rare open-capsule MOF can
easily load the largest amounts of sulfur and iodine among known MOFs.
In addition, derived from capsular-MOF and melamine through pyrolysis–phosphidation,
we fabricated a nitrogen-doped capsular carbon-based framework with
iron–nickel phosphide nanoparticles immobilized on capsular
carbons interconnected by plentiful carbon nanotubes. Benefiting from
synergistic effects between the carbon framework and highly surface-exposed
phosphide sites, the material exhibits efficient multifunctional electrocatalysis
for oxygen evolution, hydrogen evolution, and oxygen reduction, achieving
well-qualified assemblies of an overall water splitting (low potential
of 1.59 V at 10 mA·cm–2) and a rechargeable
Zn–air battery (high peak power density of 250 mW·cm–2 and excellent stability for 500 h), which afford
remarkably practical prospects over previously known electrocatalysts.