Tunable multi-color luminescence and white emission in lanthanide ion functionalized polyoxometalate-based metal–organic frameworks hybrids and fabricated thin films

Abstract

In this paper, luminescent hybrid material systems are prepared with porous polyoxometalate-based metal–organic framework (POM-based MOF)[La(H2O)4(pdc)]4}[SiMo12O40]·2H2O (1) through the introduction of lanthanide ions (Ln3+, Ln = Eu, Tb, Sm, Dy, Eu/Tb, Dy/Eu) by a solvothermal approach. The POM-based MOF serves as a host for protecting the luminescence of Ln3+ cations. The structure, thermal stability, ultraviolet absorption and visible light emission of the target hybrid materials are determined with powder X-rays diffraction patterns (PXRD), Fourier transform infrared spectra (FTIR), thermalgravimetric analysis (TGA), inductively coupled plasma-mass spectrometry (ICP-MS) analysis, energy dispersive spectrometer (EDS), ultraviolet visible diffusion reflections spectra (UV–vis DRS) and especially luminescence spectra. The final luminescence of the Ln3+ hybrids can be adjusted by changing the composition of Ln3+ cations or converting the excitation wavelengths of them. Among [La0.95Dy0.045Eu0.005(H2O)4(pdc)]4}[SiMo12O40]·2H2O (Dy3+/Eu3+@1) emits white luminescence under the excitation at 295 nm and the Commission Internationale de L'Eclairage (CIE) chromaticity coordinate of it is (0.361, 0.3408). Moreover, we manufacture POM-based MOF thin films by using ethyl methacrylate (EMA) to assemble the POM-based MOF on a quartz plate as substrate. The hybrid thin films based on {La0.95Eu0.05(H2O)4(pdc)]4}[SiMo12O40]·2H2O (Eu3+@1) and La0.95Eu0.04Tb0.01(H2O)4(pdc)]4}[SiMo12O40]·2H2O (Eu3+/Tb3+ @1) can also achieve white-light. The CIE chromaticity coordinates of them are (0.3425, 0.2548) and (0.3857, 0.3377), respectively.