Unveiling a Three Phase Mixed Heterojunction via Phase-Selective Anchoring of Polymer for Efficient Photocatalysis

The ligand-to-metal charge transfer (LMCT) facilitated activation of TiO₂ has noteworthy potential for solar energy harvesting. However, the fast back electron transfer from TiO₂ to an oxidized sensitizer is a key limiting factor causing low photocatalyst efficiency. Herein, a new catalyst design to both increase LMCT efficiency and minimize the back electron transfer is presented. A phase-selective modification of mixed-phase TiO₂ (anatase: rutile interface) with poly-salophen organic polymer is developed. The salophen and salen family organic monomers are selectively bound and polymerized on the anatase phase but not the rutile phase, which results in the formation of a three-phase system. Such a three-phase system converts an unfavorable polymer TiO₂ core-shell structure to an intimately mixed blend morphology, consisting of interfaced crystalline rutile TiO₂ and an amorphous polymer-covered anatase-phase TiO₂. The developed mixed-blend morphology poly-S@P25 can produce H₂ of 37 410 µmol h^–1 g^–1 of polymer, which is ≈3.4 times higher than core-shell poly-S@anatase TiO₂. This approach overcomes the drawback of the traditional core-shell structured system for efficient electron harvesting from the LMCT process.