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Direct Observation of Non-Radiative Thermal Relaxation with Vibrational Paddlewheel Cu−Cu Node in Metal-Organic Frameworks

Direct Observation of Non-Radiative Thermal Relaxation with Vibrational Paddlewheel Cu−Cu Node in Metal-Organic Frameworks
Song, Hye InBae, JinheeLee, Eun JiKirlikovali, Kent O.Farha, Omar K.Jeong, Nak Cheon
DGIST Authors
Jeong, Nak Cheon
Issue Date
2020 125th KCS Spring Meeting
Non-radiative thermal relaxation (NRTR), a ubiquitous process in natural and artificial molecules and materials by which excited electrons relax to the ground state through thermal, non-radiative pathways with atomic or lattice vibrations, has been extensively studied in contemporary chemistry since control of NRTR can lead to an increase in luminescence efficiency. Meanwhile, a few recent reports have shown that the control of NRTR and the resulting heat energy from NRTR can potentially benefit new applications in optoelectronics. Nevertheless, evidence for the heat energy generation of the NRTR has been poorly provided.Non-radiative thermal relaxation is mainly interpreted with atomic or lattice ‘vibrational transition’. Specifically, once visible photons are irradiated to a chemical substance, the absorbed photons will promote electrons from the ground state to excited state orbitals by electronic transition. Subsequently, some of excited electrons at high energy states can reach the spillover point, and the electrons at the spillover point can transfer back to the ground state by means of a non-radiative vibrational transition (or non-radiative thermal relaxation process). Therefore, once a small fraction of excited electrons undergoes the non-radiative vibrational transition, small quantity of heat energy can be emitted initially, and subsequently, the small heat energy can accelerate the vibrational transition for the excited electrons to reach the spillover point. As a result, the emission of heat energy can be multiplied until a substantial amount of excited electrons returns to the ground state through the non-radiative vibrational transition (i.e., NRTR).In this presentation, we provide, for the first time, direct evidence for the heat generation of the non-radiative vibrational transition process, using HKUST-1 and Cu-MOF-2 crystals with a visible 532-nm or 780-nm laser beam.
Related Researcher
  • Author Jeong, Nak Cheon Supramolecular Inorganic Chemistry Laboratory
  • Research Interests Inorganic Chemistry; Metal-Organic Framework; Nanoporous Materials; Electron Transport;Ion Transport
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Department of Physics and ChemistrySupramolecular Inorganic Chemistry Laboratory2. Conference Papers

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