Composite ZIF-8 with CQDs for boosting visible-light-driven photocatalytic removal of NO

Metal–organic frameworks (MOFs) with the advantage of high surface area are attracting growing concern in photocatalysis , but the limitations of no visible light response and low carrier migration efficiency also exist in MOFs materials. Carbon quantum dots (CQDs) with unique optical properties are a novel class of carbon nanomaterials , which have attracted extensive attention in the field of photocatalysis . In this work, compositing with CQDs for realizing MOFs visible-light photocatalytic NO performance was elucidated. We synthesized CQDs/ZIF-8 composite via a simple surface soaking approach, and the 0.5-CQDs/ZIF-8 composite showed the best removal performance of NO, which was ∼43%. The effect of CQDs on boosting visible-light photocatalytic activity of ZIF-8 was explored based on the photocurrent test, electrochemical impedance spectra, activity tests and radical trapping experiment under different monochromatic light irradiation , up-conversion photoluminescence spectra of CQDs, and electron spin resonance spectroscopy measurement. These results demonstrated compositing with CQDs is an effective way to boost the visible-light photocatalytic activity of ZIF-8, in which CQDs improves the visible light utilization and carrier separation efficiency. Apart of that, the results fully proved that the up-conversion effect indeed played a role in driving ZIF-8 into visible light response owing to the still working holes (h + ) under 500 nm of monochromatic light irradiation. The possible NO x removal mechanism over CQDs/ZIF-8 composite was then proposed in the work.