Light-Responsive Nanoemulsion-Guided Assembly of Honeycomb Hierarchically Macro/mesoporous Metal-Organic Framework...

Despite that soft template pathways are promising avenues for synthesizing hierarchically porous metal-organic framework (MOF) nanoparticles, smart-responsive-directed assembly strategies have been rarely extended to fabricate well-defined hierarchical macro/mesoporosities in MOF architectures. Herein, a novel light-responsive nanoemulsion-guided strategy is reported to prepare honeycomb hierarchically porous UiO-66 nanoparticles (UiO-66 HHPNPs) with macro/mesoporosities transition using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (F127, PEO₁₀₆PPO₇₀PEO₁₀₆) and azobenzene (Azo) as a light-responsive soft template. By facilely tuning the concentration of Azo and light irradiation (e.g., 365 nm ultraviolet light), the assembled UiO-66 HHPNPs varies from microporous architectures to macro/mesoporous dendritic architectures with an average pore size expanding from 14 to 135 nm. It is worth noting that the cis-trans configuration transformation of Azo under the irradiation of 475 nm blue light results in the shrunken micelles and thus rapid template removal from macro/mesoporous architectures of UiO-66 HHPNPs. Additionally, a light-responsive soft template can also alter the pore structures of other MOF nanoparticles (e.g., zirconium-based UiO-66). Importantly, the resultant macro/mesoporous UiO-66 HHPNPs reveal superior catalytic activity than the microporous UiO-66 HHPNPs in the 3,3',5,5'-tetramethylbenzidine catalytic reaction system. This newfangled light-induced template assembly technique paves an attractive way for the rational design of multimodal macro/mesoporous architectures and thus renders them broad applications.