Self-assembly of Pt(ii)-tetrakis(pentafluorophenyl)porphyrin via F⋯F interaction for efficient cocatalyst-free photocatalytic hydrogen evolution

Abstract

The aggregation caused quenching (ACQ) of photoluminescence in porphyrins, which is attributed to strong π–π (C⋯C/C⋯H) interactions in the solid state, often leads to a decrease in photoluminescence, short electron lifetimes (τ_PL) and inferior performance in photocatalytic hydrogen evolution (PHE). To address this issue, we explore self-assembled Pt(II)-tetrakis(pentafluorophenyl)porphyrin (SA-PtPFTPP) and Pt(II)-tetraphenylporphyrin (SA-PtTPP) as candidates. We find that SA-PtPFTPP via F⋯F interaction effectively restricts ACQ in the solid state, whereas SA-PtTPP shows noticeable ACQ due to intermolecular π–π (C⋯C/C⋯H) interactions. Compared with SA-PtTPP, SA-PtPFTPP demonstrates a longer τ_PL value and higher photoluminescence quantum yield. Moreover, SA-PtPFTPP exhibits more efficient charge separation and better dispersibility in water with a low water contact angle. The favorable photophysical properties of SA-PtPFTPP enable a direct electron transfer from the photoexcited porphyrin moiety to the proton in cocatalyst-free PHE. As a result, SA-PtPFTPP shows a much higher PHE rate (η_H2) of 400.0 μmol g⁻¹ h⁻¹ compared to SA-PtTPP (5.0 μmol g⁻¹ h⁻¹) under heterogeneous conditions. Importantly, SA-PtPFTPP also demonstrates high photostability under prolonged irradiation, as evidenced by the consistent η_H2 production in each photocycle and unchanged morphology before and after light irradiation. This research provides a valuable insight into the design of self-assembled porphyrins with hindered ACQ, offering potential applications in cocatalyst-free PHE.