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

Abstract

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.