Visible-light-driven lanthanide-organic-frameworks modified TiO2 photocatalysts utilizing up-conversion effect

Abstract Highly efficient and quite stable composite with core-shell-like architecture reported herein, responds to the challenge of sunlight-driven photocatalysts. The Ln(ndc)/TiO2 photocatalytic system comprises active lanthanide-carboxylate coordination networks (Nd, Er, Ho, and Tm as metal ions, and 2,6-naphthalene dicarboxylic acid as the organic linker) and inert titanium dioxide and allow to convert incompatible visible radiation into functional ultraviolet photons. The combination of the antenna-reactor photocatalyst complex with Ln(ndc) shell layers promotes light harvesting and efficient mass transfer, resulting in additional photoexcited electrons. The Nd(ndc) metal-organic frameworks successfully activate TiO2 via up-conversion energy transfer. The apparent quantum efficiency, determined at wavelengths corresponding to the transitions from the Nd3+ ground state, equals to 2.8% and 3.2% for 525 and 583 nm, respectively. Integration of the Nd(ndc) MOFs and TiO2 results in the highest efficiency of phenol degradation, affording a value of 87.5% after 60 min of visible light (λ > 420 nm) exposure.