Crystalline‐State Solvent: Metal‐Organic Frameworks as a Platform for Intercepting Aggregation‐Caused Quenching

• Published in: Chinese journal of chemistry Vol. 40; no. 5; pp. 589 - 596
• Main Authors: Jia, Yan‐Yuan, Yin, Jia‐Cheng, Li, Na, Zhang, Ying‐Hui, Feng, Rui, Yao, Zhao‐Quan, Bu, Xian‐He
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH & Co. KGaA 01.03.2022; Wiley Subscription Services, Inc
• Subjects: Agglomeration; Broadband; Cage compounds; Cages; Color tunability; Encapsulation; Fluorescence; In‐situ encapsulation; Metal-organic frameworks; Quenching; Rhodamine 6G; Spectral analysis; Spectral emittance; Spectrum analysis
• DOI: 10.1002/cjoc.202100712
• ISSN: 1001-604X

Comprehensive Summary The sequestration of organic luminescent molecules (OLMs) within cage‐based metal‐organic frameworks (MOFs) as a dispersion platform has been developed to impede aggregation‐caused quenching (ACQ). The homogenous encapsulation of distinct luminescent guests of different sizes and emissive behaviors in the cage structure of a MOF resulted in high fluorescent quantum yields of 44.8% for DAPI@NKU‐110 (DAPI = 4',6‐diamidino‐2‐phenylindole), 65.4% for TPPA@NKU‐110 (TPPA = tris(4‐(pyridin‐4‐ yl)phenyl)amine), 31.3% for R6G@NKU‐110 (R6G = Rhodamine 6G), and 58.3% for PY@NKU‐110 (PY = Pyronin Y), attributable to the confinement effect caused by the rigid cages of NKU‐110. More significantly, a positive correlation of the encapsulated quantity of OLMs with their concentration in the in‐situ solvothermal reaction was unveiled by spectral analysis and utilized to facilely fabricate a white‐light‐emitting crystal material TPPA+R6G@NKU‐110. This material features a large crystal size on the millimeter‐scale, broadband white emission, ideal CIE coordinates (0.33, 0.34), and a high quantum yield (49.1%) when excited at 365 nm. Moreover, such a strategy can be easily generalized to an abundance of other cage‐based MOFs and a plentiful volume of OLMs for the future development of colorful, high performance luminescent materials. We report the encapsulation of various organic luminescent molecules (OLMs) in a cage‐based MOF which acts as a solid solvent for preventing aggregation‐caused quenching, thereby creating single‐crystalline materials with high fluorescence quantum yields and excellent luminescent properties due to the confinement effect derived from the internal cages.