Ln₂(OH)₄SO₄·nH₂O (Ln = Pr to Tb;n∼ 2): A New Family of Layered Rare-Earth Hydroxides Rigidly Pillared by Sulfate Ions

Abstract

The title compounds precipitate from aqueous solutions of Ln2(SO4)3, Na2SO4, and hexamethylenetetramine (N2 atmosphere, reflux, 6 h).

Layered Rare Earth Hydroxides: Structural Aspects and Photoluminescence Properties

“…Upon heating at 200-1,000 C, the hydroxide film underwent a quasi-topotactic transformation into a film of RE 2 O 3 . The resulting oxide film was highly oriented along the (111) axis as a consequence of [39]. Copyright 2010 American Chemical Society this unique process.…”

“…These compounds isostructurally crystallize in the monoclinic phase with cell parameters a~0.63, b~0.37, c~0.84 nm, and 90.07 < β < 90. 39 . β is approximately equal to 90 , and the unit cell is subtly distorted from the orthorhombic one.…”

Recent progress in layered rare-earth hydroxide (LRH) and its application in luminescence

“…Homogeneous precipitation and hydrothermal reaction are the two main ways to obtain 241-LRHs. The former technique seems limited to intermediately sized Ln 3+ , and a series of single-phase 241-LRHs (Ln = Pr-Tb) have been synthesized through homogeneous hydrolysis of Ln sulfates in the presence of hexamethylenetetramine [8]. We recently proposed hydrothermal reaction for the controlled crystallization of 241-LRHs, using Ln nitrate and (NH 4 ) 2 SO 4 as the reactants, and successfully extended this family of compounds to the larger Ln 3+ of La and smaller Ln 3+ of Dy [24].…”

“…Due to the unique electronic, optical, magnetic, and catalytic properties of the Ln elements, the LRHs are attracting continuous attention since their emergence in 2006 [5], and extensive efforts have been paid to their synthesis, structural characterization, anion exchange, and exfoliation. Ln 2 (OH) 5 (A x ) 1/x ·nH 2 O (m = 1, n = 1-2, and typically n  1.5; termed as the 251-LRH phase) [5][6][7] and Ln 2 (OH) 4 (A x ) 2/x ·nH 2 O (m = 2, n = 0-2; 241-LRH phase) [8,9] are two important groups of the LRHs family. The anions (such as NO 3  , Cl  , and Br  ) in the 251-LRH phase of n  1.5 frequently exist in the interlayer gallery as free ones (not coordinated to the Ln 3+ center) and thus exhibit facile exchange with a wide range of carboxylate and sulfonate anions [10][11][12][13][14][15].…”

“…Therefore, the 251-LRHs may potentially be exfoliated into single-layer nanosheets of significantly two-dimensional morphologies for the further construction of various nanostructures, particularly highly transparent functional films. The 241-LRH phase, on the other hand, is rigidly pillared by the interlayer anions (typical of SO 4 2 ) [8,9], and thus exfoliation of its bulk crystals into nanosheets with the strategy applied for 251-LRHs has not been achieved. The LRHs of the 251 and 241 phases, both having Ln centers in the hydroxide host layers, represent a new class of luminescent materials.…”