Cattaneo Alice S, Ferrara Chiara, Marculescu Adriana Mossuto, Giannici Francesco, Martorana Antonino, Mustarelli Piercarlo, Tealdi Cristina
Dipartimento di Chimica Sezione Chimica-Fisica, Università degli Studi di Pavia, Via Taramelli 16, I-27000 Pavia, Italy.
Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Viale delle Scienze ed. 17, I-90128 Palermo, Italy.
Phys Chem Chem Phys. 2016 Aug 3;18(31):21903-12. doi: 10.1039/c6cp02943d.
Dion-Jacobson phases, like MLaNb2O7, are an interesting class of ion-exchangeable layered perovskites possessing electronic and photocatalytic properties. Their protonated and organo-modified homologues, in particular, have already been indicated as promising catalysts. However, the structural analysis of these highly tailorable materials is still incomplete, and both the intercalation process and thermal stability of the included organic moieties are far from being completely understood. In this study, we present a thorough solid-state NMR characterization of HLaNb2O7·xH2O intercalated with different amounts of octylamine, or with decylamine. Samples were analyzed as prepared, and after thermal treatment at different temperatures up to 220 °C. The substitution of pristine proton ions was followed via(1)H MAS NMR spectroscopy, whereas the alkyl chains were monitored through (13)C((1)H) CP MAS experiments. The interactions in the interlayer space were explored using (13)C((1)H) 2D heteronuclear correlation experiments. We demonstrate that some of the protons are involved in the functionalization reaction, and some of them are in close proximity to the alkyl ammonium chains. Heating of the hybrid materials leads first to a rearrangement of the alkyl chains and then to their degradation. The spatial arrangement of the chains, their interactions and the thermal behavior of the materials depend on the extent of the functionalization, and on the nature of the intercalated alkyl ammonium ions.
像MLaNb₂O₇这样的迪翁 - 雅各布森相是一类有趣的可离子交换层状钙钛矿，具有电子和光催化性能。特别是它们的质子化和有机改性同系物已被表明是有前途的催化剂。然而，这些高度可定制材料的结构分析仍不完整，并且插入过程和所含有机部分的热稳定性远未被完全理解。在本研究中，我们对用不同量的辛胺或癸胺插入的HLaNb₂O₇·xH₂O进行了全面的固态核磁共振表征。对制备好的样品以及在高达220℃的不同温度下热处理后的样品进行了分析。通过¹H MAS NMR光谱跟踪原始质子离子的取代，而通过¹³C(¹H) CP MAS实验监测烷基链。使用¹³C(¹H)二维异核相关实验探索层间空间中的相互作用。我们证明一些质子参与了官能化反应，并且其中一些质子与烷基铵链紧密相邻。混合材料的加热首先导致烷基链的重排，然后导致其降解。链的空间排列、它们的相互作用以及材料的热行为取决于官能化程度以及插入的烷基铵离子的性质。
