Acid-regulated hydrolysis and condensation of titanium cation toward controllable synthesis of multiphase mesoporous TiO2 for effectively enhance photocatalytic H2 evolution

Titanium dioxide (TiO 2 ) polymorphs photocatalysts containing two or more crystal phases have customarily been synthesized at high temperature using complicated procedures or expensive equipment, accompanied by the formation of by-products. Therefore, here, we propose an effective acid-regulated hydrolysis and condensation of titanium cation strategy to directly synthesize mesoporous TiO 2 with controllable phase junctions. In the method, poly dimethyl diallyl ammonium chloride (PDADMAC) is used as the structure directing agent to produce mesostructure, and hydrochloric acid (HCl) is used as the acid regulator and coordination agent to adjust the hydrolysis and condensation modes of Ti 4+ , thereby controlling the crystal structure and phase junctions of synthesized mesoporous TiO 2 polymorphs. Furthermore, since the heterophase junctions and mesostructure effectively improve the separation and transfer of photo-generated electron-holes, the obtained R 74 B 26 with unique brookite and rutile phase junctions owns the highest photocatalytic activity among all obtained samples, the evolution rate of H 2 is 8.98 mmol h ‐1−1 g −1 . This work will open up new perspectives toward the synthesis of mesoporous polycrystalline material for various potential applications. • Acid-regulated hydrolysis and condensation of titanium cations method is proposed to construct multiphase mesoporous TiO 2 . • PDADMAC acts as a pore-forming gent to produce radially divergent mesopores. • Mesoporous TiO 2 with rutile and brookite phase exhibits enhanced photocatalytic H 2 evolution rate （8.98 mmol h -1 g -1 ）. • The mechanism of H 2 evolution is discussed.