MOF-derived core/shell C-TiO2/CoTiO3 type II heterojunction for efficient photocatalytic removal of antibiotics

Highlights: • Core/shell C-TiO₂/CoTiO₃ type II heterojunction was synthesized by MOF-derived method. • C-TiO₂/CoTiO₃ shows excellent photocatalytic degradation and TOC removal of CIP. • The • OH is the main radical species in the photocatalytic degradation of CIP. • A new approach and insight for the synthesis of core/shell heterojunction was proposed. A novel core/shell C-TiO₂/CoTiO₃ type II heterojunction was successfully synthesized via a direct calcination method by using MIL-125/Co core-shell nanocakes as a sacrificial template and precursor. In the calcination process, the organic ligand in MIL-125 acts as an in-situ carbon doping source to form a carbon-doped TiO₂ core (C-TiO₂). At the same time, CoTiO₃ nanoparticles are formed on the surface of C-TiO₂ by an in-situ solid-state reaction between the C-TiO₂ and Co²⁺ shell of MIL-125/Co. Due to such delicate core/shell structural features, carbon doping and type II heterojunctions, C-TiO₂/CoTiO₃ core/shell composites can effectively harvest visible light, facilitate the interfacial separation and suppress the recombination of photogenerated electron-hole pairs, leading to the remarkable photocatalytic activity for removal of ciprofloxacin (CIP). In particular, C-TiO₂/CoTiO₃-3 exhibits the best photocatalytic degradation activity of CIP with a degradation efficiency of 99.6% and a total carbon content removal percentage of 76% under visible-light illumination for 120 min. In addition, the proposed photocatalytic mechanism study illustrated that the main radical species in the photocatalytic degradation of CIP using C-TiO₂/CoTiO₃ as the photocatalyst is • OH. This work provides a new approach and insight for synthesizing core/shell heterojunction-based photocatalysts for various applications.