Fabrication of surface molecularly imprinted photocatalyst POPD/Bi2O3/CeO2 with selective denitrification performance under visible light irradiation

Abstract

Enhancing photocatalytic selectivity is essential for the effective and efficient utilization of catalysts. In this study, a molecularly imprinted polymer POPD/Bi₂O₃/CeO₂, designated as MIP-POPD/Bi₂O₃/CeO₂, was successfully synthesized via photopolymerization using pyridine as a template. The resulting MIP-POPD/Bi₂O₃/CeO₂ was characterized through Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N₂ adsorption–desorption isotherms, and UV–vis diffuse reflectance spectroscopy. MIP-POPD/Bi₂O₃/CeO₂ exhibited enhanced charge transfer and efficient separation of photogenerated carriers, as confirmed by photoluminescence measurements, electrochemical impedance spectroscopy analysis, and photocurrent response (I–t) curve evaluations. When the concentration of pyridine in simulated oil reached 80 µg/g, with an amount of 1.6 g/L for MIP-POPD/Bi₂O₃/CeO₂ and an illumination time of 120 min, the degradation rate of pyridine achieved 80%, which is 1.57 times greater than that observed using NMIP-POPD/Bi₂O₃/CeO₂. After an adsorption for 30 min, MIP-POPD/Bi₂O₃/CeO₂ exhibited the adsorption capacity of 5 mg/g, attributed to the large number of molecularly imprinted pores on its surface. In various mixed systems, the selectivity coefficients for pyridine using MIP-POPD/Bi₂O₃/CeO₂ consistently exceeded 1.5, which can be attributed to the selective adsorption properties of the imprinted pores within the polymers that preferentially recognize and remove pyridine. Furthermore, after five cycles, the photocatalytic degradation rate of pyridine by MIP-POPD/Bi₂O₃/CeO₂ can still reach 77%, indicating that MIP-POPD/Bi₂O₃/CeO₂ possesses good stability. Trapping experiments demonstrated that superoxide radicals (·O₂⁻) and holes (h⁺) were the predominant active species in photocatalytic reactions. Additionally, a proposed mechanism for photocatalytic denitrification utilizing MIP-POPD/Bi₂O₃/CeO₂ was presented. This study provides a promising strategy for designing Bi-based molecular imprinting photocatalysts aimed at efficiently removing low-concentration, highly toxic target pollutants from mixed samples.