The Zr8O6 Secondary Building Unit and Porphyrin Linker Catalyze Light‐Driven H2 Evolution in Porphyrin‐Based Metal Organic Frameworks

The four Zr 8 O 6 ‐based metal‐organic frameworks (MOFs), porous coordination network (PCN) 221 M, comprising earth‐abundant metalloporphyrin tetracarboxylate (M‐TCPP, M: 2 H, Zn, Ni, and a mixture of 1:1 Zn and Ni), are investigated for light‐driven H 2 evolution reaction (HER) in water. Under the irradiation of a 405 nm light emitting diode source and in the presence of triethanolamine (TEOA) as a sacrificial electron donor, the photocatalytic HER activity of PCN 221 varies with the metal center in the porphyrin linker. Among the tested MOFs, the Zn‐porphyrin derivative (PCN 221 Zn) produces H 2 at a TON = 4, which is about seven times greater than that of homogeneous Zn‐TCPP (0.6) and superior to its 2 H (2.7), Ni (0.40), and ZnNi (1.6) analogs. Detailed photochemical studies via time‐resolved and steady‐state spectroscopy reveal two distinct charge transfer pathways: Direct H 2 evolution from Zn‐TCPP itself, and electron transfer from the Zn‐TCPP photosensitizer to the Zr 8 O 6 SBU catalytic sites. The improved HER performance of PCN 221 Zn is attributed to its favorable features, such as optical absorption, excited‐state properties, and charge separation dynamics, as well as the coordination of TEOA. This study provides fundamental insights into the design of MOF‐based heterogeneous photocatalysts exploiting earth‐abundant metal‐based porphyrin for solar fuel generation.