Novel N/Carbon Quantum Dot Modified MIL-125(Ti) Composite for Enhanced Visible-Light Photocatalytic Removal of NO

Abstract

Highly efficient and stable photocatalysts were synthesized at room temperature by modifying MIL-125(Ti) with N-doped carbon quantum dots (N/CM(Ti)). The N/ CM(Ti) with 2.5 vol % N doped carbon quantum dots (N/CQDs) had the best light absorption and visible-light photocatalytic nitrogen oxide (NO) removal efficiency (approximately 49%). It was found through X-ray photoelectron spectroscopy analysis that a N−Ti−O bond was formed in the 2.5 vol % N/CM(Ti), which is more conducive to charge transfer. Photocurrent and electrochemical impedance data also showed that the carrier separation efficiency of 2.5 vol % N/CM(Ti) was significantly superior to that of . In addition, the Ti III −Ti IV of MIL-125(Ti) acts as the active center for photocatalytic removal of NO. Two possible electron migration paths were proposed: electron transfer from N/ CQDs to Ti III −Ti IV center of MIL-125(Ti) due to the photoinduced electron transfer property of N/CQDs, and absorption of UV light generated from the N/CQDs by the terephthalic acid ligand followed by electron transfer to metal active sites for photocatalytic removal of NO.

Visible-Light-Promoted Photocatalytic Applications of Carbon Dots: A Review

“…synthesized a composite MIL-125­(Ti)/N-CQD as N/CM­(Ti) at room temperature and shows NO removal under visible-light with ∼49% efficiency. Figure c shows the NO removal with different catalysts as control MIL-125­(Ti) and different loaded N-CQD in N/CM­(Ti) composite . Huang et al reported the NOx removal and NO 2 production using photocatalyst CQD/ZnFe 2 O 4 composite that has significantly better activity (∼8 times) than that of ZnFe 2 O 4 because of rapid charge transfer and generation of reactive species (O 2 •– and • OH) under irradiation of visible light (λ > 420 nm) as shown in Figure d,e .…”

“…(c) MIL-125­(Ti) and N/CM­(Ti) composites with 0.25, 2.5, and 5.0 vol % loading of N/CQD under visible light. Reproduced from ref . Copyright 2020 American Chemical Society.…”

Recent Advances in the Application and Mechanism of Carbon Dots/Metal‐Organic Frameworks Hybrids in Photocatalysis and the Detection of Environmental Pollutants

“…Nitrogen oxides (NOx) have varying degrees of toxicity to human health and natural environment, and have become an increasingly serious global problem [49] . Chen and co‐workers [50] constructed highly efficient and stable photocatalysts by modifying MIL‐125 (Ti) with N‐doped carbon quantum dots (CDs@MIL‐125 (Ti)) for photocatalytic removal of NO (Figure 4b). Under light conditions, CDs@MIL‐125 (Ti) photocatalysts can catalyze NO to produce nitrate (NO 3 − ) and visible‐light photocatalytic nitrogen oxide (NO) removal efficiency (approximately 49%).…”

“…Adapted from reference [48] with permission, copyright 2018 Elsevier. (b) A schematic illustration of N/CQDs/MIL-125(Ti) composite for photocatalytic removal of NO.Adapted from reference[50] with permission, copyright 2020 American Chemical Society.…”

Metal–Organic Frameworks for NOx Adsorption and Their Applications in Separation, Sensing, Catalysis, and Biology

“…In the photocatalytic reaction over MIL-125 (Ti). Reproduced with permission [143]. Copyright 2020, American Chemical Society.…”