Single-Phase White-Light Phosphors Based on a Bicarbazole-Based Metal–Organic Framework with Encapsulated Dyes

Single-phase phosphors are promising materials for the
production
of new white-light-emitting diodes (WLEDs), whereas efficient white-light-emitting
phosphors with high color rendering index (CRI) values still remain
rare. Herein, we report a new metal–organic framework (MOF)
[Zn4O(BCTA)1.5] (BUT-119) with high porosity
and intense blue photoluminescence emission, which is constructed
from a bicarbazole-based ligand, 4,4′,4″,4‴-(9,9′-bicarbazole-3,3′,6,6′-tetrayl)tetrabenzolate
(BCTA4–), and Zn4O cluster. The simultaneous
encapsulation of a red-emitting dye, Rhodamine B (RhB) or Basic Red
2 (BR), and a green-emitting dye, Acriflavine (AF), into the pores
of BUT-119 results in two single-phase white phosphors, AF/RhB@BUT-119
and AF/BR@BUT-119, showing bright and warm white light emission with
high quantum yields (22% and 19%) due to efficient energy transfer
among the MOF host and the guest dye molecules. Noteworthily, the
CRI values of AF/RhB@BUT-119 and AF/BR@BUT-119 are high up to 94,
higher than those of previously reported white-light-emitting MOF-based
materials, suggesting their high potential in the fabrication of WLEDs.

单相荧光粉（Single-phase phosphors）是制备新型白光发光二极管（WLEDs）的极具应用前景的材料，但兼具高效发光与高显色指数（CRI）的单相白光荧光粉仍较为稀缺。本文报道了一种兼具高孔隙率与强蓝色光致发光性能的新型金属有机框架（MOF）[Zn₄O(BCTA)₁.₅]（命名为BUT-119），其构筑基元为双咔唑基配体4,4′,4″,4‴-(9,9′-双咔唑-3,3′,6,6′-四基)四苯甲酸盐（BCTA⁴⁻）与Zn₄O簇。将红色发光染料罗丹明B（RhB）或碱性红2（BR）与绿色发光染料吖啶黄（AF）同时封装至BUT-119的孔道中，可得到两种单相白光荧光粉AF/RhB@BUT-119与AF/BR@BUT-119。得益于MOF主体与客体染料分子间的高效能量转移，这两种材料均展现出明亮的暖白光发射，量子产率分别可达22%与19%。值得注意的是，AF/RhB@BUT-119与AF/BR@BUT-119的显色指数最高可达94，优于此前报道的基于MOF的白光发光材料，表明其在白光LED制备中具有极高的应用潜力。