The effect of metal distribution on the luminescence properties of mixed-lanthanide metal–organic frameworks

Abstract

A series of lanthanide metal-organic frameworks (MOFs) of the general formula [Ln(Hodip)(HO)]·nHO (Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Er, 6; Hodip = 5,5'-oxydiisophthalic acid) have been prepared and shown crystallographically to have isostructural three-dimensional frameworks. The fluorescence emission spectra of the europium compound 2, which is red, and the terbium compound 4, which is green, show characteristic peaks for transitions involving the metal centres, whereas that for the gadolinium compound 3 is dominated by transitions involving Hodip. Using a 1 : 1 : 1 mixture of europium, gadolinium and terbium nitrates in the synthesis resulted in the mixed-metal MOF [GdTbEu(Hodip)(HO)]·nHO 7, for which the ratio of the metal ions was determined using EDX spectroscopy. The fluorescence emission spectrum of 7 is dominated by europium emission bands reflecting the higher proportion of Eu centres and quenching of the terbium fluorescence by metal-to-metal energy transfer. A series of core-shell MOF materials based on the Ln(Hodip)(HO) framework have been prepared in order to isolate the lanthanides in different domains within the crystals. The emission spectra for materials with Gd@Tb@Eu (8) and Tb@Eu@Gd (9) are dominated by terbium emissions, suggesting that physical separation from europium suppresses quenching. In contrast, the material with Eu@Gd@Tb (10) shows only broad ligand bands and europium emissions. This confirms that core-shell MOFs have different fluorescence properties to simple mixed-metal MOFs, demonstrating that the spatial distribution of the metals within a mixed-lanthanide MOF affects the fluorescence behaviour.

Bimetallic metal–organic frameworks and their derivatives

“…Mahon, Burrows and co-workers studied the effect of metal distribution on the luminescence properties of mixed LnMOFs. 201 Solid solution mixed LnMOFs, [Gd 0.17 Tb 0.19 Eu 0.64 (-Hodip) (H 2 O)]$nH 2 O (H 4 odip ¼ 5,5 0 -oxydiisophthalic acid), showed an emission spectrum with strong bands of Eu 3+ and weak bands of Tb 3+ and H 4 odip. This is due to the energy transfer from Tb 3+ to Eu 3+ , resulting in a quenching of Tb 3+ transitions.…”

Coordination of a Potentially Tritopic Ligand via Phosphorus, Nitrogen and Oxygen: From Ligand Design to Heterobimetallic Metal–Organic Frameworks and Supramolecules

“…Progress in the chemistry concerned with metal−organic frameworks (MOFs) has accelerated rapidly over the last few decades and shows no sign of slowing down. 1−7 Tailored materials for specialized applications are developed by the hour, targeting catalysis, 8,9 optics, 10,11 electronics, 12 gas storage, 13,14 drug delivery, 15 pest management, 16 decontamination, 17 and cunningly both explosives 18 and shock absorbents. 19 While the majority of these fields of research use monometallic compounds, a small yet increasing number of publications deal with the selective incorporation of two or more metal species in the same compound.…”

Three Lanthanide Metal‐Organic Frameworks Based on an Ether‐Decorated Polycarboxylic Acid Linker: Luminescence Modulation, CO2 Capture and Conversion Properties

“…On the other hand, the ether O group in H 4 L can be regarded as a potential active site for the adsorption and conversion of CO 2 . In some known MOFs, H 4 L displays strong coordinated ability with various metal ions, including d‐ and p ‐block ions as well as some Ln 3+ ions, in which H 4 L reveals rich coordinated modes, and corresponding MOFs possess photoactive, magnetic and luminescent sensing properties . In this paper, three new isostructural 3D Ln‐MOFs, {H[LnL(H 2 O)]⋅2 H 2 O} n ( 1‐Ln , Ln=Eu 3+ , Gd 3+ and Tb 3+ ), have been constructed, which contain 1D channels decorated by the exposed ether O atoms and open metal sites.…”

“…Li, Q.-X. Hu, Prof. L. Hou, Prof. Y.-Y.Lc an be regarded as ap otential active site for the adsorption and conversion of CO 2 .I ns ome known MOFs, H 4 L displays strong coordinated ability with variousm etal ions, including d-and p-block ions as well as some Ln 3 + ions, in which H 4 Lr eveals rich coordinated modes, and corresponding MOFs possess photoactive, magnetic and luminescents ensing properties [35][36][37][38]. In this paper,t hree new isostructural 3D Ln-…”