Electric-Field-Mediated Electron Tunneling of Supramolecular Naphthalimide Nanostructures for Biomimetic H₂ Production

The design and synthesis of two semiconducting bis (4-ethynyl-bridging 1, 8-naphthalimide) bolaamphiphiles (BENI-COO⁻ and BENI-NH₃⁺) to fabricate supramolecular metal–insulator–semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H₂ evolution rate of ca. 3.12 mmol g⁻¹⋅h⁻¹ and an apparent quantum efficiency (AQE) of ca. 1.63 % at 400 nm were achieved over the BENI-COO⁻-NH₃⁺-Ni MIS photosystem prepared by electrostatic self-assembly of BENI-COO⁻ with the opposite-charged DuBois-Ni catalysts. The hot electrons of photoexcited BENI-COO⁻ nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an alkyl region of 2.2–2.5 nm length at a rate of 6.10×10⁸ s⁻¹, which is five times larger than the BENI-NH₃⁺ nanoribbons (1.17×10⁸ s⁻¹). The electric field benefited significantly the electron tunneling dynamics and compensated the charge-separated states insufficient in the BENI-COO⁻ nanofibers.