Encapsulating low-coordinated Pt clusters within a metal-organic framework induces spatial charge separation boosting photocatalytic hydrogen evolution

Pt nanoparticles (NPs) can enhance the photocatalytic performance of metal-organic frameworks (MOFs) for hydrogen evolution. However, Pt atoms in the core of Pt NPs cannot be utilized for the hydrogen evolution reaction (HER) and the agglomeration of Pt NPs also reduces the enhancement effect. In this paper, we propose a simple and kinetically modulated post-synthetic strategy to encapsulate low-coordinated and monodispersed Pt clusters (PCs) with a mean size of 1.6 nm into the inner space of NH2-UiO-66 (U6N). The X-ray absorption spectroscopy (XAS) data indicate that the PCs with low coordination numbers and short Pt-Pt bonds possess more unoccupied d orbitals, which enhance the interactions between PCs and the MOF. Consequently, such enhanced interactions result in the acceleration of electron-hole separation that is beneficial to the HER activity of U6N, as confirmed by ultrafast transient absorption spectra. This MOF with encapsulated PCs shows a H2 production efficiency of 36.83 mmol h-1 g-1 and turnover number of 598 h-1 under visible light with photosensitizer erythrosin B and sacrificial agent triethanolamine. The results suggest that such PCs can efficiently boost the photocatalytic HER of U6N, and our strategy may provide a new avenue for fabricating MOFs with excellent catalytic properties.