MOF/TiO2 erythrocyte-like heterostructures decorated by noble metals for use in hydrogen photogeneration and pollutant photodegradation

Abstract

Various metal–organic framework (MOF)/TiO₂ heterostructures can be obtained by the partial hydrolysis or calcination of Ti-based MOFs. By adjusting the hydrolysis and calcination steps of NH₂-MIL-125 (Ti), a novel photoactive material composed of a MOF (NH₂-MIL-125 (Ti)) and TiO₂, with a unique “erythrocyte” shape, was developed. Furthermore, modification of the composition prepared by the partial hydrolysis of NH₂-MIL-125 (Ti) (h-MOF) using Au, Ag, Pt, or Pd metal nanoparticles resulted in a significant increase in the efficiency of hydrogen photogeneration. Higher photocatalytic properties are associated with the excitation of MOFs and TiO₂, electron transfer, and electron accumulation on nanoparticles. Using the optimal h-MOF/Au photocatalyst, 117 μmol g⁻¹ h⁻¹ of hydrogen was produced. On the other hand, composites (ch-MOFs) obtained by calcination of h-MOFs after modification with Au showed high efficiency in the photodegradation of phenol under the threshold of visible radiation (over 42 μmol dm⁻³ h⁻¹). These properties are related to the generation of electrons by Au nanoparticles because of the corresponding localized surface plasmon resonance. This results in the formation of reactive oxygen species (hydroxyl and superoxide radicals) that decompose organic pollutants. Overall, the obtained materials have high porosity and photocatalytic stability, which are important for photocatalytic processes.