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

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 H-2 production (ca. 925 and 827 mu mol 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 mu mol 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)(.)