Electric-Field-Mediated Electron Tunneling of Supramolecular Naphthalimide Nanostructures for Biomimetic H 2 Production.

The design and synthesis of two semiconducting bis (4-ethynyl-bridging 1, 8-naphthalimide) bolaamphiphiles (BENI-COO ^- and BENI-NH ₃ ⁺ ) to fabricate supramolecular metal-insulator-semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H ₂ 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 ^- -NH ₃ ⁺ -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 6.10×10 ⁸  s ^-1 , which is five times larger than the BENI-NH ₃ ⁺ nanoribbons (1.17×10 ⁸  s ^-1 ). The electric field benefited significantly the electron tunneling dynamics and compensated the charge-separated states insufficient in the BENI-COO ^- nanofibers.
(© 2020 Wiley-VCH GmbH.)