Highly dispersed Pt clusters encapsulated in MIL-125-NH₂ via in situ auto-reduction method for photocatalytic H₂ production under visible light

Efficient hydrogen production via photocatalysis with high utilization efficiency of Pt cocatalyst is of great importance for sustainable development. In this work, we report an in situ auto-reduction strategy to encapsulate highly dispersed Pt clusters inside the cages of MIL-125-NH₂. The amino groups in MIL-125-NH₂ first react with formaldehyde to form reducing groups (i.e., –NH-CH₂OH), which can in situ auto-reduce the confined Pt²⁺ ions to ultrasmall Pt clusters within the cavities. With optimized Pt content, photocatalytic H₂ production over the obtained Pt(1.5)/MIL-125-NH-CH₂OH catalyst with 1.43 wt.% Pt loading achieved as high as 4, 496.4 µmol·g⁻¹·h⁻¹ under visible light (λ > 420 nm) due to the facilitated transfer and separation of the photo-induced charger carriers arising from the synergetic effects between highly dispersed Pt clusters and MIL-125-NH-CH₂OH framework. This in situ auto-reduction strategy may be extended to encapsulate various kinds of metal or alloy clusters/nanoparticles within amino-functioned metal-organic frameworks (MOFs) with superior properties and excellent performance.