ON‐OFF Switching of Photocatalytic Hydrogen Evolution by Built‐in Pt‐Nitrogen‐Carbon Reticular Heterojunctions.

Cognigni, Leonardo; Gobbato, Thomas; Benazzi, Elisabetta; Paoloni, Lorenzo; Vizio, Biagio Di; Bonetto, Ruggero; Rigodanza, Francesco; Bonetto, Alessandro; Agnoli, Stefano; Bonchio, Marcella; Costa, Paolo

COF engineering with a built‐in, high concentration of defined N‐doped sites overcomes the "black‐box" drawback of conventional trial‐and‐error N‐doping methods (used in polymeric carbon nitride and graphene), that hamper a directed evolution of functional carbon interfaces based on structure‐reactivity guidelines. The cutting‐edge challenge is to dissect the many complex and interdependent functions that originate from reticular N‐doping, including modification of the material optoelectronics, band alignments, interfacial contacts and co‐localization of active‐sites, producing a multiple‐set of effectors that can all play a role to regulate photocatalysis. Herein, an ON‐OFF gated photocatalytic H2 evolution (PHE) is dictated by the Pt‐NPyridine‐carbon active sites and probed with a dual COF platform, based on stable β‐ketoenamine connectivities made of triformylphloroglucinol (Tp) as the acceptor knots and 1,4‐diaminonaphtalene (Naph) or 5,8‐diaminoisoquinoline (IsoQ) as donors. Our results showcase two novel COF‐Naph‐Tp and COF‐IsoQ‐Tp frameworks featuring quasi‐identical slip‐stacked microporous structure, and similar surface area, band gap, light harvesting envelope up to 700 nm, fluorescence emission profile/lifetime, and PEIS response at the surface/water interface (Rct=16–10±4 KΩ). A divergent behaviour is indeed observed for COF‐IsoQ‐Tp with record photoelectrochemical outputs (J=−16 μA cm−2, Rt=3 KΩ at 0.40 V vs RHE) and two orders of magnitude higher rate of PHE (11.3 mmol g−1 h−1, λ>400 nm, pH 5) compared to the inactive COF‐Naph‐Tp analogue. It turns out that PHE is regulated by the isoquinoline residues at the COF pores where emergent Pt‐NPyridine‐carbon functional heterojunctions are formed upon photo‐deposition of Pt nanoparticles as co‐catalysts, as probed by combined XPS and DFT calculations evidence. This work sets a key guideline to direct the design of carbon‐based materials encoding the installation of metal‐nitrogen‐carbon active sites within tailored coordination environments enabling the catalytic performance.

BAND gaps; PHOTOCATALYSIS; ISOQUINOLINE; SURFACE area; GRAPHENE

ChemSusChem, 2025, Vol 18, Issue 5, p1

1864-5631

Academic Journal

10.1002/cssc.202401977