Ag nanoparticles encapsulated in mixed-valence NH2-MIL-101(FeII/III) for high-efficiency photocatalytic N2 fixation

To improve the photocatalytic efficiency of N2 fixation to produce NH3, herein, Ag nanoparticles (NPs) encapsulated NH2-MIL-101(FeII/III) with mixed-valence was fabricated. A higher oxygen vacancy concentration was observed in NH2-MIL-101(FeII/III) compared to NH2-MIL-101(Fe). The Schottky junction between NH2-MIL-101(FeII/III) and Ag NPs effectively promoted the migration and separation of the photogenerated carriers, while the localized surface plasmon resonance effect of Ag NPs enhanced the light absorption and facilitated the generation of hot electrons. Consequently, the resulting Ag@NH2-MIL-101(FeII/III) delivered an excellent photocatalytic N2 fixation activity with high stability. The optimal ammonia yield of Ag@NH2-MIL-101(FeII/III) under visible light was 244.6 µmol g−1 h−1, 1.9 and 3.2 folds that of NH2-MIL-101(FeII/III) and NH2-MIL-101(Fe), receptivity. Finally, with the aid of in situ infrared spectrometry, the intermediate products and reaction pathway were investigated. [Display omitted] •Ag NPs encapsulated NH2-MIL-101(FeII/III) with mixed-valence was fabricated.•The resultant Ag@NH2-MIL-101(FeII/III) can efficiently reduce N2 to NH3.•The maximum NH3 yield reached 244.6 μmol·g−1·h−1 under visible light.•Enhanced activity due to the synergy of mixed-valence active sites and LSPR of Ag.•Possible mechanism of N2 fixation was investigated by in situ FT-IR spectroscopy.