Molecular-Linked Z-Scheme Heterojunction of Ti³⁺-Doped TiO₂ and WO₃ Nanoparticles for Photocatalytic Removal of Acetaldehyde

Photocatalytic removal of indoor organic air pollutants is effective, but there are practical limits to catalytic activation by indoor conditions. Here, we report a molecular-linked heterojunction of semiconducting metal oxide nanoparticles (e.g., Blue TiO₂ and WO₃) that can be activated by wide-range light including an indoor light-emitting diode (LED) under ambient conditions. Chemically reduced Blue TiO₂ improves visible light absorption of white TiO₂ by regulating the electronic structure with self-doping of Ti³⁺. The heterojunction between Blue TiO₂ and WO₃ is formed via a molecular linker, and a hybridized electronic structure of a molecular-linked Z-scheme alignment is generated without changes in chemical characteristics, increasing utilization of indoor light and effectively improving electron-hole separation. WO₃ sufficiently adapts to the photooxidative degradation of air pollutants by ^•OH, while Blue TiO₂ leads to the effective generation of ^•O₂^-, leading to the complete decomposition of gaseous acetaldehyde (CH₃CHO) to CO₂ and CO without remaining organic byproducts (e.g., formaldehyde). As a robust interfacial contact, molecular-linked heterojunctions provide efficient charge separation and highly stable performance and enhance solution-processable homogeneous coatings of metal oxide photocatalysts on real surfaces.