Pure-blue light-emitting diodes play a critical role in solid-state lighting and full-color display technologies as they are indispensable for achieving broad color gamuts and high color-rendering index lighting. However, the development of high-performance perovskite light-emitting diodes (PeLEDs) with pure-blue electroluminescence presents a significant challenge, particularly in terms of attaining a high brightness, spectral stability, and quantum efficiency. This research demonstrates the effectiveness of incorporating 4-aminobenzophenone (4-ABP) as a novel passivating agent into blue perovskite emitting layers (EMLs) to effectively mitigate defective antisites and enhance pure-blue emission properties. The carbonyl and amino groups of 4-ABP provide dual-functional sites for hydrogen bonding and Lewis acid-base interactions, thereby significantly passivating defects within the perovskite EMLs while simultaneously influencing crystallization kinetics. Consequently, the incorporation of 4-ABP reduces defect sites, suppresses nonradiative recombination, and facilitates carrier transport and injection, resulting in a high luminance of 787.68 cd m and a maximum external quantum efficiency (EQE) of 4.17%, outperforming control devices. The pure-blue PeLEDs passivated with 4-ABP achieve pure-blue EL emission at 460 nm with a full width at half-maximum bandwidth of 22.42 nm, which realizes CIE chromatic coordinates of (0.139, 0.038), covering a prime blue color gamut according to the Rec.2020 standard. Notably, these devices exhibit excellent spectral and operational stability under voltage bias due to efficient defect passivation, which suppresses ion migration channels.