Encapsulation of an iridium complex in a metal–organic framework to give a composite with efficient white light emission

Abstract

We successfully synthesized a novel anionic luminescent metal–organic framework (MOF) (NENU-524) with a lonsdaleite topology. NENU-524 contains a trigonal prismatic unit {Zn₈(btca)₆(2-NH₂-bdc)₃} that can be regarded as a double secondary building unit with an unusual triply bound triangular frustum geometry. The prepared NENU-524 had a permanent porosity and excellent stability in air. NENU-524 was used as a platform to encapsulate yellow-emitting [Ir(ppy)₂(bpy)]⁺ cations in the nanotube channels of the blue-emitting MOF via an ion-exchange process. The [Ir(ppy)₂(bpy)]⁺@NENU-524 MOF ([Ir(ppy)₂(bpy)]⁺ concentration 3.86 wt%) emitted a pure white light with CIE coordinates of (0.300, 0.336) and a high quantum yield of up to 15.2%. The white light-emitting diodes assembled using [Ir(ppy)₂(bpy)]⁺@NENU-524 as a white phosphor emitted a bright white light, suggesting that the composite is a promising material for use in lighting. The assembled white light-emitting diodes continued to emit a bright white light for up to one month. This simple and feasible approach could be used to develop luminescent luminophor@MOFs composites for practical applications.