The structural, phonon and optical properties of [CH3NH3]M0.5CrxAl0.5−x(HCOO)3 (M = Na, K; x = 0, 0.025, 0.5) metal–organic framework perovskites for luminescence thermometry. Issue 15 (29th March 2019)

• Record Type: Journal Article
• Authors: Ptak, Maciej; Dziuk, Błażej; Stefańska, Dagmara; Hermanowicz, Krzysztof
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 15(2019)
• Page Start: 7965
• Page End: 7972
• Publication Date: 2019-03-29
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c9cp01043b
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : We report the structural, phonon and optical properties of perovskite-type heterometallic formates templated by methylammonium cations. Abstract : We report the structural, phonon and luminescence studies of six heterometallic perovskite-type metal–organic frameworks (MOFs) templated by methylammonium cations (CH3 NH3 + and MeA + ) with the following formulae: [MeA]Na0.5 Cr0.5 (HCOO)3 (MeANaCr), [MeA]K0.5 Cr0.5 (HCOO)3 (MeAKCr), [MeA]Na0.5 Al0.5 (HCOO)3 (MeANaAl), [MeA]K0.5 Al0.5 (HCOO)3 (MeAKAl), [MeA]Na0.5 Cr0.025 Al0.475 (HCOO)3 (MeANaAlCr, 5 mol% of Cr 3+ ions) and [MeA]K0.5 Cr0.025 Al0.475 (HCOO)3 (MeAKAlCr, 5 mol% of Cr 3+ ions). All of them crystallise in a monoclinic system ( P 21 / n space group) with one MeA + cation in an asymmetric unit forming four medium-strength hydrogen bonds (HBs) with a metal-formate framework. The DSC measurements and XRD single-crystal studies show that the studied crystals do not undergo structural phase transitions in the 100–440 K range. The high tolerance factors indicate that there is not enough space for the re-orientational motions of the MeA + cations, explaining the lack of the structural phase transitions. We also present IR and Raman studies supported by the factor group analysis together with luminescence properties. We have shown that the strength of the crystal field parameter ( D q / B ) varies in the 2.13–2.56 range depending on the chemical composition of the studied compounds. We show that perovskite-like formate MOFs with Na + (K + ) ions can be considered as potential candidates for non-contact thermometry in the 225–400 K (325 K) range.