Thienoacene‐Based Conjugated Porous Polymer/TiO2 Hybrids as Photocatalysts in Artificial Photosynthesis

• Published in: Advanced sustainable systems (Online) 2024-02, Vol.8 (2), p.n/a
• Main Authors: López‐Calixto, Carmen G., Gomez‐Mendoza, Miguel, Barawi, Mariam, Collado, Laura, Liras, Marta, de la Peña O´Shea, Víctor A.
• Format: Article
• Language: English
• Subjects: artificial photosynthesis; charge transfers; conjugated porous polymers; thienoacenes
• ISSN: 2366-7486; 2366-7486
• DOI: 10.1002/adsu.202300330

Herein, the design and synthesis of a couple of CPPs based on thienoacene units (named as IEP‐14 and IEP‐15, stand for IMDEA Energy Polymer numbers 14 and 15) are described, which show high BET surface areas, good photo(thermal) stabilities, and appropriate electronic alignment with TiO2 to prepare hybrids (named as IEP‐x@T‐10, X = 14 and 15, being 10 wt% of polymer loading). It is shown that the simultaneous UV–vis irradiation of both materials leads to better H2 production (ca. 925 and 827 µmol g−1 h−1 by IEP‐15@T‐10 and IEP‐14@T‐10, 12 and 11‐fold higher production than bare TiO2) than the solely irradiation at visible of the CPPs (ca. 124 and 90 µmol g−1 h−1 by IEP‐15@T‐10 and IEP‐14@T‐10 when TiO2 is photocatalytically inactive). The reason is attributed to the charge‐transfer mechanisms that occur between the counterparts of the hybrid material: in the first case it consists in a Z‐scheme charge transfer mechanism, while in the second one is a sensitization charge transfer mechanism. Both mechanisms are elucidated by advanced techniques. Furthermore, in a gas phase CO2 photoreduction test, IEP‐15@T‐10 shows sixfold higher CH4 evolution than TiO2, which result in a selectivity shift from CO to CH4 (i.e., >26% greater selectivity than bare TiO2). Artificial photosynthesis is a challenging energy solution for the conversion of sunlight into solar fuels. Hybrid heterostructures, composed by thienoacenes‐based conjugated porous polymers and TiO2, show remarkable production of electron‐demanding products in CO2 photoreduction and high H2 evolution from water. Photophysical studies reveal the creation of a Z‐scheme charge transfer mechanism that leads to longer carrier lifetimes and a higher driving force for electron transfer in artificial photosynthesis.