Alkyl-linked TiO2@COF heterostructure facilitating photocatalytic CO2 reduction by targeted electron transport

Abstract

Targeted electron transfer to catalytically active site for CO₂ reduction is promising for enhancing the efficiency of artificial photosynthesis. Here, we demonstrate a design of an alkyl-linked heterostructure composing of TiO₂ and a Cu-porphyrin-based covalent organic framework (TiO₂@CuPorTT-COF) for the photoreduction of CO₂ with H₂O. Through specific coordination effect, the alkyl chain bridges TiO₂ and Cu moiety in COF. Upon light illumination, the photoinduced electrons in TiO₂ can be directionally transported across the interface along the alkyl chain to the Cu active sites to reduce adsorbed CO₂, while the left holes are consumed by the H₂O oxidation, enhancing the spatial separation and utilization of electron-hole pairs. Accordingly, the TiO₂@CuPorTT-COF enables remarkably superior catalytic activities over the counterpart without the alkyl bridge for electron transfer with 5 times of CO production rate. An apparent quantum efficiency of 0.455% at 380 nm is achieved. Moreover, a dynamic evolution of Cu active site for CO₂ reduction is revealed, which can be promoted by the targeting electron transport approach. This work provides a targeted electron transport strategy for constructing photocatalysts.