Quasi-In Situ Synthesis of Ag NPs@m-MIL-100(Fe) for the Enhanced Photocatalytic Elimination of Flowing Xylenes.

The implantation of metal nanoparticles (MNPs) into metal-organic framework (MOF) hosts is a promising means to prepare high-performance photocatalysts for the degradation of gas pollutants. However, the uniform encapsulation of MNPs in MOFs is still challenging. Herein, a facile "quasi-in situ" encapsulation method is proposed by utilizing the spatial confinement effect of the colloidal network formed during the synthesis of the MIL-100(Fe) monolith [noted as m-MIL-100(Fe)]. Highly dispersed Ag NPs with an average diameter of ∼2 nm are encapsulated in the MIL-100(Fe) monolith to form a unique "watermelon-seed" structure, which ensures the large contact area between the two components and protects Ag NPs from being oxidized. The fast charge transfer between m-MIL-100(Fe) and Ag NPs enables the spatial separation of electron-hole pairs and promotes the generation of oxidative radicals. Compared with pristine m-MIL-100(Fe), the 0.2 wt % Ag@m-MIL-100(Fe) composite shows obviously enhanced photodegradation efficiencies for flowing o-xylene under both xenon (∼97%) and visible light (∼80.0%) with high stability. This work not only provides a promising Ag@m-MIL-100(Fe) material for eliminating air pollutants but also gives a versatile means for the design and synthesis of nanoparticles@MOFs composites with desired performance.