Halide Replacement with Complete Preservation of Crystal Lattice in Mixed‐Anion Lanthanide Oxyhalides

Abstract

Ac hallenge in anion control in periodic solids is to preserve the crystal lattice while substituting for different anions of widely varying sizea nd hardness.P ost-synthetic modification routes that place cations or anions in nonequilibrium configurations are promising;h owever,s uch methods remain relatively unexplored for anion placement. Here,w er eport the synthesis of LaOI nanocrystals by an onhydrolytic sol-gel condensation reaction and their transformation into LaOBr,LaOCl, and LaOF nanocrystals along hardsoft acid-base principles using post-synthetic metathesis reactions with ammonium halides.A nion displacement proceeds along halide planes,p reserving the tetragonal matlockite structure.E nergy-variant X-raye xcited optical luminesce signatures of alloyed Tb 3+ -ions is asensitive quantum reporter of the preservation of the cation sublattice and hardening of the crystal structure upon anion replacement.

Evidence for enormous iodide anion migration in lanthanum oxyiodide–based solid

“…The I − ions in the distinctive I − layer are expected to migrate in the ab plane. Recently, topotactic anion exchange in LaOI was reported, suggesting the iodide ion diffusion in the lattice ( 35 ). In addition to its suitable structure for ion conduction, LaOI has significantly high thermal and chemical stabilities than the simple iodide (LaI 3 ) ( 36 ).…”