Well-distributed Pt-nanoparticles within confined coordination interspaces of self-sensitized porphyrin metal–organic frameworks: synergistic effect boosting highly efficient photocatalytic hydrogen evolution reaction† †Electronic supplementary information (ESI) available: Details of comparison of H2 evolution rates of different MOF composites, general information, physical characterization, chemical stability study, photocatalytic reactions, mechanistic study. CCDC 1920896. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc01866b

An effective strategy for the fabrication of an efficient HER photocatalyst of Pt@Pd-PCN222(Hf) has been reported.
Effective conversion of solar energy into chemical energy by visible light represents a potential strategy for sustainable development. Among which, photocatalytic hydrogen evolution reaction (HER) with a relatively small activation energy (1.23 eV, around 1000 nm light irradiation) is especially attractive. In this work, well-distributed platinum nanoparticles (Pt-NPs) with a width of about 3 nm have been successfully immobilized into the confined coordination interspaces of 3.7 nm diameter, which are facilitated by early transition metal Hf(iv)-based clusters of a self-sensitized palladium porphyrin metal–organic framework. Under visible light irradiation, the resultant Pt@Pd-PCN-222(Hf) (which is also denoted as Pt@Pd-PMOF-2(Hf)) displays superb photocatalytic activity, achieving an unprecedented maximum H2 evolution rate of 22 674 μmol g–1 h–1 with a turn-over number (TON) of 4131.2 in 32 h and the highest turn-over frequency (TOF) of 482.5 h–1 based on Pt-NPs. This photocatalyst can be recycled and reused for three successive runs without significant loss of catalytic activity. This effective strategy takes advantage of the synergetic effect between Pd-porphyrin photosensitizers and Pt-NP co-catalysts confined within nanoscale coordination interspaces incorporating hydrophilic Hf(iv)-oxo clusters.