Defect engineering and synergistic interfaces are critical structural factors for catalytic oxidation, yet the role of a Oᵥ–Ti3+–Pt triadic interface remains unexplored in MXene-induced TiO₂ (MTO) for formaldehyde (HCHO) oxidation. In this study, a novel Pt/MTO catalyst was synthesized by leveraging defect-controlled anatase MTO, followed by 0.1% Pt impregnation under N₂/H₂ annealing. Structural analysis confirmed the formation of anatase TiO₂ enriched with oxygen vacancies (Oᵥ–Ti3+) whose concentration and distribution are tuned by the annealing atmosphere, thereby influencing crystallinity, Pt particle size, and oxidation state. Importantly, in MTO, the Oᵥ–Ti3+–Pt interface establishes strong, directional electronic coupling, enabling charge delocalization between Ov-Ti3+ defect states and Pt surface atoms unlike conventional oxygen-vacancy–noble-metal systems where vacancies act mainly as anchoring sites. The coexistence of Oᵥ sites and abundance of defect-induced onsite-OH (Ov-H) groups creates a synergistic interface with Pt nanoparticles, facilitating strong electronic coupling and active site availability. In situ DRIFTS revealed that Pt sites promote O₂ dissociation, while Oᵥ–Ti3+ rich defects serve as adsorption sites for HCHO. Meanwhile, intrinsic lattice hydroxyls (OL-H) promote H₂O dissociation to generate Ov-H groups which accelerate the oxidation of formate intermediate directly to CO2, bypassing the carbonate pathway. These cooperative effects—between defect-rich MTO, well-dispersed Pt, and Oᵥ–H interfaces—reflect quantum phenomena such as electron localization–delocalization and quantum confinement, significantly boosting catalysis. Consequently, Pt/MTO-N2 achieved 98.2% HCHO removal (10 ppm) within 100 min, with steady CO₂ generation at a WHSV of 150,000 cm3·h−1·g_cat−1. This work highlights a strategy for localized defect confinement and elucidates how Oᵥ-driven structures modulate catalytic kinetics in HCHO oxidation.