2 research outputs found
Synthesis, Crystal Structures, and Luminescence Properties of Carboxylate Based Rare-Earth Coordination Polymers
Rare-earth coordination polymers or lanthanide–organic
frameworks
with hitherto unreported crystal structures have been obtained on
the basis of the “light” lanthanides Pr, Nd, Sm, and
Eu in combination with terephthalic acid and using a slightly altered
literature synthesis procedure. Rietveld refinement has shown that
powder XRD patterns of such compounds are largely dominated by the
positions of the heavy elements, pointing to isostructural networks
for all four terephthalate-based materials. An in-depth luminescence
study has been performed on the reported MOFs, showing rare praseodymium
and samarium emission in the visible spectrum, aside from the strong
europium luminescence and the near-infrared emission from both a terephthalate
and 2,5-pyridinedicarboxylate based neodymium-MOF
Bipyridine-Based Nanosized Metal–Organic Framework with Tunable Luminescence by a Postmodification with Eu(III): An Experimental and Theoretical Study
A gallium 2,2′-bipyridine-5,5′-dicarboxylate
metal–organic
framework, GaÂ(OH)Â(bpydc), denoted as COMOC-4 (COMOC = Center for Ordered
Materials, Organometallics and Catalysis, Ghent University) has been
synthesized via solvothermal synthesis procedure. The structure has
the topology of an aluminum 2,2′-bipyridine-5,5′-dicarboxylate
– the so-called MOF-253. TEM and SEM micrographs show the COMOC-4
crystals are formed in nanoplates with uniform size of 30–50
nm. The UV–vis spectra of COMOC-4 in methanol solution show
maximal electronic absorption at 307 nm. This results from linker
to linker transitions as elucidated by time-dependent density functional
theory simulations on the linker and COMOC-4 cluster models. When
excited at 400 nm, COMOC-4 displays an emission band centered at 542
nm. Upon immersion in different solvents, the emission band for the
framework is shifted in the range of 525–548 nm depending on
the solvent. After incorporating Eu<sup>3+</sup> cations, the emission
band of the framework is shifted to even shorter wavelengths (505
nm). By varying the excitation wavelengths from 250 to 400 nm, we
can fine-tune the emission from red to yellowish green in the CIE
diagram. The luminescence behavior of Eu<sup>3+</sup> cations is well
preserved and the solid-state luminescence lifetimes of Ď„<sub>1</sub> = 45 ÎĽs (35.4%) and Ď„<sub>2</sub> = 162 ÎĽs
(64.6%) are observed