Highly Efficient Self-Trapped Bluish White-Light Emission from [Pb4Cl5]3+ Nodes in a Moisture-Tolerant Metal-Organic Framework

Abstract

Highly luminescent zero-dimensional (0D) metal halide clusters attract widespread attention owing to strong exciton confinement and populated self-trapped states but often exhibit narrow emission and are susceptible to hydrolysis. Herein, we demonstrate a moisture-resistant metal-organic framework (MOF) consisting of cationic 0D [Pb4Cl5]3+ nodes bridged by adamantanetetracarboxylate. Upon near-UV excitation, the material emits intrinsic broadband bluish white-light emission with high external quantum efficiency of 35% and a color rendering index of 76. Unlike organoammonium cations in lead perovskites, the Pb-carboxylate coordination affords the MOF to be chemically stable and photo-stable in high humidity. The photoemitter exhibits undiminished photoemissions under ambient conditions [∼60% relative humidity (RH)] upon continuous UV irradiation (143 mW/cm2, 365 nm) for 7 days. The insertion of [Na4Cl]3+ moieties will connect 0D units into two-dimensional (2D) metal halide layers to limit structural strain and decrease the quantum efficiency from 35% to 15%, confirming the key importance of 0D units for efficient emission.