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Near-ultraviolet (NUV) light is critical for applications in lighting, manufacturing, and medical fields, yet existing NUV emitters often suffer from complex syntheses or rely on toxic or unsustainable materials. Herein, we present a facile solvothermal synthesis of high-efficiency, narrow-band NUV-emitting carbon dots (NUV-CDs) derived from bio-derivable phloroglucinol. These NUV-CDs exhibit a sharp emission peak at 403 nm with a high photoluminescence quantum yield (PLQY) of 60 % and a narrow full width at half maximum (FWHM) of 35 nm in ethanol solution. Structural and spectroscopic analyses reveal that the NUV-CDs are formed through dehydration and dehydrogenation reactions, resulting in a single type of emissive center with weak environmental interactions. When integrated into a polyvinyl alcohol (PVA) matrix and applied as a light-conversion coating on a UV-LED chip, the resulting device emits at 408 nm with an FWHM of 50 nm and an exceptional color purity of 87.7 %. This study offers a promising, environmentally friendly alternative for high-performance NUV light sources, complementing the spectral gap of existing CD materials.