ZIF-8 self-etching method for Au/polydopamine hybrid cubic microcapsules with modulated nanostructures

Metal-organic framework (MOF)-derived nanostructures exhibit wonderful characteristics and possess broad application potential by modulating the complex composition and inner nanostructure. Although various MOF-based nanocomposites have been successfully developed, a facile method that can easily modulate the structure-dependent chemical components of the MOF-derived hybrids remains a challenge. By coating zeolitic imidazolate framework-8 (ZIF-8) with Au/polydopamine (Au/PDA) via in situ redox-oxidation polymerization of HAuCl₄ and dopamine, it was found that the ZIF-8 templates were simultaneously etched off to give Au/PDA hybrid microcapsules with a cubic shape. This one-step sacrificial templating process followed a competing chelation between gold ions and Zn²⁺ cations to 2-methylimidazole and PDA; thus, both the hollow and the yolk-like hybrid cubic microcapsules were controllably obtained by varying the synthetic dynamics. Owing to the hollow nature, penetrated PDA shell, well-distributed Au nanocrystals, and unique stable nanostructure, the non-spherical Au/PDA hybrid cubic microcapsules showed high performance in catalyzing the reduction of 4-nitrophenol as well as adsorption/release of ibuprofen as a model drug. Moreover, this simple strategy offers a controllable design in developing multifunctional nanocomposites with definite inner nanostructures and activities for nanocatalysis, drug delivery, energy storage etc.