Bifunctional color-tuning luminescent Ln@Zr-MOFs for white LEDs and sensitive, ultrafast detection of nitrobenzene in aqueous media

Abstract

Rapid and quantitative detection of nitrobenzene (NB) in wastewater is of great significance to protect the natural environment and human health. In this work, bifunctional Ln@Zr-MOFs based on UiO-66 were successfully fabricated by partially replacing terephthalic acid (H₂BDC) ligands with m-phthalic acid (m-H₂BDC) ligands and post-synthetic modification (PSM) with Ln³⁺ (Ln³⁺ = Eu³⁺, Tb³⁺). The “antenna effect” of the m-H₂BDC ligands makes Ln@Zr-MOFs exhibit the characteristic emissions of Ln³⁺. By adjusting the amount and type of Ln³⁺, controllable color-tuning emissions can be easily realized, which endows them with a great application prospect for white LEDs. On the other hand, Eu₁₀@Zr-MOFs can serve as a turn-off fluorescent switch of NB because the red emission from Eu³⁺ can be easily quenched by NB through a photoinduced electron transfer (PET) process between NB and its ligands, and as a result, NB is successfully recognized. Particularly, Eu₁₀@Zr-MOFs as a fluorescent probe have shown many appealing properties, such as high sensitivity (limit of detection is 1.04 μM, limit of quantification is 3.48 μM, and K_sv = 24459.71 M⁻¹), quick response (less than 60 s), a broad response window (0–180 μM), excellent selectivity, and strong anti-interference ability. The real detection results of NB concentration in natural water samples have demonstrated that the reported Eu₁₀@Zr-MOFs are a potential fluorescent material that can precisely and sensitively perform fluorescence sensing of NB.