| Oct 16, 2025 |
New chiral MOF boosts circularly polarized light to record intensity
Scientists built a chiral metal-organic framework that boosts circularly polarized light, achieving record luminescence and offering a new design path for optical materials.
(Nanowerk News) A research team has developed a new class of chiral metal-organic frameworks (CMOFs) that emit light with a strong circular polarization—an optical property valuable for advanced displays, data storage, and sensing technologies. By combining a chiral rare-earth framework with luminescent guest molecules, the team achieved one of the highest known levels of circularly polarized luminescence (CPL) in such materials.
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Chiral metal-organic frameworks are crystalline structures that can emit circularly polarized light when designed with the right molecular components. The researchers focused on building these frameworks using rare-earth ions, which are known for their efficient light emission, and chiral imidazolium carboxylic ligands, which help transfer both energy and chirality through the framework. The positively charged framework channels can host negatively charged guest molecules, enabling precise control over the material’s optical behavior.
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| Schematic diagram of the preparation procedure for CPL-active rare-earth CMOFs, and |glum| amplification method. (Image: Reprinted from DOI:10.26599/POM.2025.9140095, CC BY)
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The team synthesized mirror-image versions of terbium-based CMOFs by coordinating homochiral imidazolium carboxylic acids with Tb³⁺ ions. These frameworks showed clear CPL activity, with a luminescence dissymmetry factor (|glum|) of 0.016—evidence that the chiral ligands successfully transferred their handedness to the overall structure.
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The researchers then introduced luminescent MnCl₄²⁻ anions into the chiral framework, forming a new pair of host-guest materials. This modification led to a dramatic boost in CPL performance, with |glum| values reaching 0.071, more than four times higher than the original material. “This dramatic amplification is attributed to synergistic interactions between the chiral Tb³⁺ framework and MnCl₄²⁻ guest species, which facilitate energy transfer and promote the generation of circularly polarized emission,” said Professor Jian Zhang, the study’s corresponding author.
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Spectroscopic analysis confirmed that the chirality of the ligands transferred through metal coordination, gradually forming helical chains and layered frameworks. The team also observed an additional optical signal suggesting that hydrogen bonding between the framework and guest molecules contributes to chiral transfer at the molecular level.
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To confirm the mechanism behind the enhanced luminescence, the researchers synthesized control samples that replaced either the guest or the host components. They found that the emission spectrum of one control sample overlapped with the absorption of another, supporting the idea that energy transfer between the framework and the guest molecules drives the CPL amplification.
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“This work provides a rare example of CPL enhancement in rare-earth-based CMOFs through modular host–guest engineering,” said Professor Zhang. “It also offers a general design principle for tuning the chiroptical performance of porous materials.”
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The study, published in Polyoxometalates ("Circularly polarized luminescence enhancement in rare-earth MOFs due to framework chirality and host–guest energy transfer"), establishes a promising strategy for designing next-generation luminescent materials that combine chirality, tunable emission, and structural versatility.
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