Lead‐Based Metal‐Organic‐Framework Engineering Enables the Efficiency of Pure‐Red Perovskite CsPbI ₃ Quantum Dot‐Based Light‐Emitting Diodes Exceeding 30%

CsPbI 3 quantum dots (QDs) are promising for meeting the Rec. 2020 specified red emission but still face the issue of color impurity caused by QD polydispersity. Here we develop a facile approach to synthesize nearly monodisperse and sub‐5 nm‐sized CsPbI 3 QDs by regulating QD growth using a lead‐based metal‐organic framework (Pb‐MOF). The multidentate ligands, 2‐mercapto‐4‐methyl‐5‐thiazoleaceticacid (MMA), released from the Pb‐MOFs strongly adsorb onto the QD surface through double‐end coordination with exposed Pb 2+ , effectively reducing non‐radiative recombination centers. Moreover, the QDs synthesized with Pb‐MOFs show a full width at half maximum (FWHM) of 31 nm and high conductivity (1.3 × 10 −4 S m −1 ), which are about 10 nm narrower, and 2.5‐fold higher than that of the control QDs, respectively. As a result, the QD‐based light‐emitting diodes (QLEDs) based on CsPbI 3 QDs emits at 634 nm with a CIE coordinate of (0.70, 0.30), covering 98.5% of the Rec. 2020 standard in the CIE 1931. Meanwhile, the QLEDs show a high external quantum efficiency of 30.8% and a long operational half‐lifetime ( T 50 ) exceeding 140 h at an initial luminance of 100 cd m −2 , ranking as one of the most efficient and stable pure‐red perovskite QLEDs reported to date.