Redox-active hybrid titanium dioxide with diaminopropane functionality for synergistic adsorption–catalysis of gaseous formaldehyde

Efficient removal of formaldehyde (FA) under practical conditions remains challenging because of limitations in common remediation tools, such as low FA adsorption capacity and/or poor charge separation efficiency under weak illumination (visible or ultraviolet (UV)). To overcome these challenges, a redox-active organic-inorganic hybrid system has been developed by modifying titanium dioxide (TiO 2 ) with diaminopropane (DAP). The resulting DAP/TiO 2 composite is integrated into a prototype air purifier (AP) and operated under low UV light intensity (25.9 ​W ​m −2 ) at a flow rate of 160 ​L ​min −1 . Mechanistic studies reveal that the amine (-NH 2 ) groups in DAP enhance FA adsorption and facilitate electron accumulation at the lowest unoccupied molecular orbital (LUMO), promoting superoxide radical formation. Concurrently, DAP induces oxygen vacancies and surface band bending on TiO 2 , improving charge separation and generating highly oxidizing holes. The optimal 1%-DAP/TiO 2 delivers performance metrics far surpassing those of pure TiO 2 , including a clean air delivery rate of 23.3 ​L ​min −1 , a kinetic rate of 0.84 ​mmol ​h −1 ​g −1 at a 10% removal efficiency (RE), and a mass-normalized apparent quantum yield of 0.106 molecules photon −1 g −1 . This superior activity is supported by density functional theory simulation, which reveals that DAP adsorption on oxygen-deficient TiO 2 surfaces successfully induces band-edge shifts and surface hydroxylation to enhance photocatalytic mechanism. Ultimately, these findings provide a rational design strategy for hybrid photocatalysts and mechanistic insights necessary for practical FA abatement in indoor air purification. • Diaminopropane-modified titanium dioxide (DAP/TiO 2 ) is prepared as a redox-active hybrid system. • DAP/TiO 2 is fitted into a portable air purifier (AP) to remove formaldehyde (FA) in air. • DAP adsorption on TiO 2 enhances photocatalysis via band shifts and OH formation. • Band bending drives hole migration to the surface, enhancing FA oxidation efficiency. • Formaldehyde removal efficiency reaches 100 ​% with a clean air delivery rate of 23.3 ​L ​min −1 .