Eu@COK-16, a host sensitized, hybrid luminescent metal–organic framework

Abstract

A new concept of luminescent host-guest materials was developed by introduction of Eu(3+) into COK-16, a HKUST-1 type hybrid metal-organic framework (MOF) with cation exchange properties. In Eu@COK-16, the luminescent ion resides in the pore system of the MOF. The luminescence properties of Eu@COK-16 have been studied based on excitation and emission, allowing analysis of intramolecular energy-transfer processes from the COK-16 host to the exchanged Eu(3+) ions. Both the framework trimesate (BTC) and encapsulated [PW12O40](3-) ions contribute to energy transfer. Since the antenna molecules (BTC) are part of the framework structure and [PW12O40](3-) ions only partly occupy one of the three types of cavities in the structure, a large fraction of the pore volume in this host sensitized luminescent MOF remains available for catalysis applications or adsorption of additional sensitizing molecules. The material structure was determined from a combination of elemental analysis, XAS, XRD, electron and luminescence spectroscopy.

Luminescent Layered Double Hydroxides Intercalated with an Anionic Photosensitizer via the Memory Effect

“…This indicated that the number of sites occupied by Eu 3+ increased after calcination. Compared to the 5 D 0 → 7 F 1 transition, the higher intensity of the 5 D 0 → 7 F 2 transition was enabled by forced electric dipole [45][46][47][48], which indicated the absence of inversion symmetry around the average Eu 3+ site.…”

Hierarchical COK-X Materials for Applications in Catalysis and Adsorptive Separation and Controlled Release

“…The assembly of the MOF proceeds by initial formation of POM-encapsulating cages, which connect in space to for the microporous MOF. Encapsulation of the POM not only enables room temperature synthesis of Cu 3 (BTC) 2 MOF but also protects the structure against degradation in heated, humid conditions (Mustafa et al, 2011) and provides it with cation exchange properties (Bajpe et al, 2013), enabling its conversion into a photoluminescent material by incorporation of rare earth ions and exploiting the metal-organic framework as sensitizer (Mustafa et al, 2014). By adding cetyltrimethylammonium bromide (CTAB) to the synthesis as secondary structure-directing agent, it was discovered that the aggregation sequence of the elemental cages could be altered.…”

Mesostructuring layered materials: self-supported mesoporous layered double hydroxide nanotubes

“…In agreement with the EXAFS results, this clearly rules out the octahedral symmetry commonly observed for the metal sites in LDHs. For noncentrosymmetric crystal fields, the mixing of electronic configurations with opposite parity caused by the odd components of the ligand field partially relaxes the Laporte rule, leading to non-vanishing 4f-4f dipole strengths and increased radiative transition rates 63,64 . Additionally, since the intensity of the (Eu 3+ ) 5 D0→ 7 F1 transition is host-independent, its tabulated radiative transition rate (𝐴 𝑀𝐷 = 14.73 𝑛 3 s -1 ) can used to experimentally determine the total radiative transition probability (A 𝑟𝑎𝑑 ) related to the (Eu 3+ ) 5 D0→ 7 F1,2,4 emissions based on the integral intensities (optical power or spectral irradiance, S1,2,4) and barycentre (λ1,2,4) of the (Eu 3+ ) 5 D0→ 7 F1,2,4 emission bands as:…”