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.