Rational design of honeycomb-like APTES-TiO2/COF heterostructures: Promoted intramolecular charge transfer for visible-light-driven catalytic CO2 reduction

Abstract

Utilizing organic structures to combine with TiO2 is regarded as a potent strategy for meliorating the photocatalytic performance of TiO2. Nonetheless, exploration towards the impact of modulation at organic molecular level for the COF construction (e.g., the types, substituent group and the arrangement of the building blocks), upon the optical or/and electronic features of TiO2-COF heterostructures is relatively scarce. Herein, a nitrogen-rich covalent organic framework (COF) which is employed to covalently integrate with aminopropyltriethoxysilane modified TiO2 (APTES-TiO2) through Schiff-base reaction. Due to the significant charge density disparity between the two building units, 2, 4, 6-tris (4-aminophenyl)-1, 3, 5-triazine (TAPT) and melem in the hybridized TiO2@TMP-COF with honeycomb-like morphology, the promoted intramolecular charge transfer (ICT) brings about accelerated charge delivery efficiency within the heterostructure by contrast to the structure-similar COF established hybrid, TiO2@TM-COF, which is built by the identical approach except for the involvement of TAPT monomer. Accordingly, the photocatalytic CO2 reduction reaction (CO2RR) dominated by TiO2@TMP-COF affords the CO production of 6.76 μmol·g−1·h−1, about 3 times that of TiO2@TM-COF; still, the enhanced catalytic efficiency than either the constituent TiO2 or TMP-COF owes much to the Z-scheme charge migration dynamics and augmented light-capturing capability within the hybrid. Our study opens a new landscape of heterostructure establishment for simultaneously ameliorating light absorption and accelerating charge delivery in photocatalysis.