Regulating Planarized Intramolecular Charge Transfer for Efficient Single-Phase White-Light Emission in Undoped Metal-Organic Framework Nanocrystals

The technology of combining multiple emission centers to exploit white-light-emitting (WLE) materials by taking advantage of porous metal-organic frameworks (MOFs) is mature, but preparing undoped WLE MOFs remains a challenge. Herein, a pressure-treated strategy is reported to achieve efficient white photoluminescence (PL) in undoped [Zn(Tdc)(py)]n nanocrystals (NCs) at ambient conditions, where the Commission International del'Eclairage coordinates and color temperature reach (0.31, 0.37) and 6560 K, respectively. The initial [Zn(Tdc)(py)]n NCs exhibit weak-blue PL consisting of localized excited (LE) and planarized intramolecular charge transfer (PLICT) states. After pressure treatment, the emission contributions of LE and PLICT states are balanced by increasing the planarization of subunits, thereby producing white PL. Meanwhile, the reduction of nonradiative decay triggered by the planarized structure results in 5-fold PL enhancement. Phosphor-converted light-emitting diodes based on pressure-treated samples show favorable white-light characteristics. The finding provides a new platform for the development of undoped WLE MOFs.

Multicomponent Anti-Kasha's Rule Emission from Nanotubular Metal-Organic Frameworks for Selective Detection of Small Molecules

The peak photoluminescence (PL) of conventional fluorophores is independent of the excitation wavelength (called Kasha's rule), while the search of metal-organic framework materials with the so-called anti-Kasha's rule emission remains very limited. Herein, we report the observation of anti-Kasha's rule emission in a multicomponent PL three-dimensional nanotubular metal-organic framework (abbr. MOF-NT), [Zn(μ-L)(μ-bix)]_n·0.33nH₂O [H₂L = biphenyl-3,5-dicarboxylic acid; bix = 1,4-bis(imidazole-1-ylmethyl)benzene]. The MOF-NT crystalline sample represents a notable example of strong excitation-dependent fluorescence from the ultraviolet to the visible spectral region. Moreover, by virtue of electronic flexibility and high PL efficiency, MOF-NT shows a discriminative PL response between isomeric nitroaromatic compounds. The work demonstrated the intrinsic anti-Kasha's rule emission in the crystalline-state MOF materials, providing new visions for the development of advanced solid-state emissive materials.

Applications of MOFs as Luminescent Sensors for Environmental Pollutants

The environmental pollution has become a serious issue because the pollutants can cause permanent damage to the DNA, nervous system, and circulating system, resulting in various incurable diseases, such as organ failure, malformation, angiocardiopathy, and cancer. The effective detection of environmental pollutants is urgently needed to keep them far away from daily life. Among the reported pollutant sensors, luminescent metal-organic frameworks (LMOFs) with tunable structures have attracted remarkable attention to detect the pollutants because of their excellent selectivity, sensitivity, and recyclability. Although lots of metal-organic framework (MOF)-based luminescent sensors have been summarized and discussed in previous reviews, the detection of environmental pollutants, especially radioactive ions and heavy metal ions, still have not been systematically presented. Here, the sensing mechanisms and construction principles of luminescent MOFs are discussed, and the state-of-the-art MOF-based luminescent sensors of environmental pollutants, including pesticides, antibiotics, explosives, VOCs, toxic gas, toxic small molecules, radioactive ions, and heavy metal ions are highlighted. This comprehensive review may further guide the development of luminescent MOFs and promote their practical applications for sensing environmental pollutants.

A stable luminescent zinc–organic framework as a dual-sensor toward Cu2+ and Cr2O72−, and excellent platform-encapsulated Ln3+ for systematic color tuning and white-light emission

A stable three-fold interpenetrated framework (Zn-MOF), showing chemical sensing for Cu²⁺ and Cr₂O₇²⁻, tunable luminescence and white-light emission after encapsulating lanthanide cations, was synthesized and characterized.

Synthesis, structure and luminescence properties of two Cd(ii)/M(i) (M = K, Rb) interpenetrated heterometallic frameworks based on giant double-walled cages

Two isostructural 2-fold interpenetrated double-walled frameworks based on a rare heterometallic nested cage-within-cage motif were synthesized.

Layer-structured coordination polymers based on 5-(1H-tetrazol-5-yl)isophthalic acid: structure, sensitization of lanthanide(iii) cations and small-molecule sensing

Compound 1 can serve as a host for encapsulation of Ln³⁺ ions.

An unprecedented organic–inorganic hybrid material with an I3O3 framework based on cadmium hydroxide and in situ generated 1H-tetrazolate-5-acetic acid

A novel I³O³ hybrid framework was generated, based on a rare ths inorganic subnet of cadmium hydroxide and 3-D organic network linked by tza²⁻ ligands and Cd(ii) centers.

Luminescent MOF material based on cadmium(ii) and mixed ligands: application for sensing volatile organic solvent molecules

A luminescent MOF was constructed by employing a mixed ligands strategy and may be used as a potential luminescent probe for the detection of acetone.

Solvatochromic and application in dye-sensitized solar cells of sandwich-like Cd(ii) complexes: supramolecular architectures based on N1,N3-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine

Co-sensitizers 1 and 2 exhibited solvatochromism and fluorescence quenching behavior to CH₃OH.

A highly connected (5,5,18)-c trinodal MOF with a 3D diamondoid inorganic connectivity: tunable luminescence and white-light emission

A highly connected (5,5,18)-c trinodal MOF featuring a 3D diamondoid inorganic connectivity was synthesized. Tunable color and white light emission can be achieved by inclusion of Eu³⁺ into the framework.

Chiral template induced homochiral MOFs built from achiral components: SHG enhancement and enantioselective sensing of chiral alkamines by ion-exchange

A homochiral anionic framework built from achiral components was synthesized for enantioselective sensing of chiral alkamines. Ion-exchange with polar or chiral organic cations leads to the enhancement of the SHG efficiency.

Luminescent metal–organic frameworks for chemical sensing and explosive detection

This review provides an update on the photoluminescence properties of LMOFs and their utility in chemical sensing and explosive detection.

Three novel zinc(ii) metal–organic frameworks based on three tetrazolate ligands: synthesis, structures and photoluminescence

Three metal–organic frameworks were synthesized by the reactions of Zn(NO₃)₂·6H₂O and three similar tetrazolate ligands.

White light emission based on a single component Sm(iii) framework and a two component Eu(iii)-doped Gd(iii) framework constructed from 2,2′-diphenyl dicarboxylate and 1H-imidazo[4,5-f][1,10]-phenanthroline

1D frameworks were constructed from 2,2′-diphenyl dicarboxylate and 1H-imidazo[4,5-f][1,10]-phenanthroline. White light emission was realized by Sm(iii) or Eu(iii)-doped Gd(iii) frameworks.