TiO 2 -Modulated tetra(4-carboxyphenyl)porphyrin/perylene diimide organic Z-scheme nano-heterojunctions for efficient visible-light catalytic CO 2 reduction.

Developing efficient Z-scheme heterojunctions with wide visible-light responsive perylene diimide (PDI) is highly desired for CO 2 conversion, while the effective charge transfer and separation are crucial. Herein, TiO 2 -modulated tetra(4-carboxyphenyl)porphyrin/perylene diimide (T-TP/PDI) organic nano-heterojunctions have been fabricated for CO 2 reduction, in which TP and PDI are first assembled via π-π interactions between their similar 2D conjugate structures, and then the TiO 2 nanoparticles ( ca. 10 nm) are anchored as an energy platform through the carboxyl groups on TP. The optimal one exhibits a ∼10-fold enhancement in photocatalytic activity compared with the pristine PDI. Based on the time-resolved surface photovoltage responses, electron paramagnetic resonance signals, in situ diffuse reflectance infrared Fourier transform spectra and the amount evaluation of H 2 O 2 as the water-oxidation intermediate, it is suggested that the exceptional photoactivity be ascribed to the accelerated charge transfer and separation resulting from the constructed Z-scheme nano-heterojunctions with intimate interfacial interactions and the introduced energy platform TiO 2 oriented towards largely inhibiting the type-II charge transfer pathway. This work diversifies the strategies for constructing efficient organic Z-scheme heterojunctions, and provides insight into interface correlation among components.