Atomically dispersed Pt sites on porous metal–organic frameworks to enable dual reaction mechanisms for enhanced photocatalytic hydrogen conversion

We report a porous metal–organic framework loaded with single Pt atoms, namely PCN-222(Pt) nanorods, which are prepared by the self-assembly of Pt-metalized tetrakis(4-carboxyphenyl)porphyrin ligand with a Zr6 cluster. The mass-loading of Pt in the synthesized PCN-222(Pt) is up to 4.67%, and can be accurately controlled by using an in-situ reaction strategy. Remarkably, the PCN-222(Pt) exhibits a highly efficient photocatalytic hydrogen production rate of 614 μmol g-1h−1, which is 7.4 times higher than that of PCN-222 (an isostructural sample to PCN-222(Pt) without coordinated Pt ions in the porphyrin rings). The apparent quantum efficiency of PCN-222(Pt) reaches up to 1.049% at 420 nm. Electron paramagnetic resonance spectra confirm the as-formed intermediate ZrIII, obtained from the reduction of ZrIV species, participates in the photocatalytic reaction. Density functional theory calculations demonstrate the positive role that single Pt atoms in PCN-222(Pt) play in optimizing the corresponding hydrogen binding energy. The existence of this dual reaction mechanism in PCN-222(Pt) greatly and synergistically boosts the photocatalytic H2 production activity.