1 research outputs found
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 τ<sub>1</sub> = 45 μs (35.4%) and τ<sub>2</sub> = 162 μs
(64.6%) are observed