Polyoxometalate-based metal-organic framework NENU-5 hybrid materials for photoluminescence tuning by introducing lanthanide ions and their functionalized soft ionogel/thin film

Polyoxometalate-based metal-organic framework (POM-MOF) hybrid materials have received increasing attention, and have the advantages of both POMs and MOFs. Herein, we encapsulate lanthanide(III) (Ln(3+)) cations (Eu3+, Tb3+, Sm3+ and Dy3+) in the channels of [Cu-2(BTC)(4/3)(H2O)(2)](6)[HPMo12O40] center dot (C4H12N)(2) center dot xH(2)O (x = 25-30, NENU-5) nanocrystals by exchanging the (C4H12N)+ with Ln(3+). The structure, composition, thermal stability, morphology, and absorption of ultraviolet and visible light of the obtained hybrids are characterized by PXRD, ICP, FTIR, SEM and UV-vis DRS. The photophysical properties of these materials are investigated in detail under ultraviolet radiation, displaying the characteristic emission line of the corresponding Ln(3+) ions. These physical characterizations prove that these hybrid materials exhibit a uniform mesoporous structure, good crystallization and multi-color luminescence. Furthermore, photofunctional Ln(3+) functionalized POM-MOF hybrids are dispersed in an ionic liquid compound (1-(2-hydroxyethyl)-3-methylimidazolium bromide) which has little effect on luminescence to produce a soft ion gel. Finally, we manufacture their thin films by assembling the hybrids on a quartz plate using a polymer linker to achieve further practical application. Both the fluorescence of lanthanide hybrid materials and that of thin films can be adjusted by different Ln(3+) compositions or excitation wavelengths and finally reach white light output.