Issue 21, 2022

Synthesis and structural characterisation of solid titanium(iv) phosphate materials by means of X-ray absorption and NMR spectroscopy

Abstract

Solid titanium phosphate, TiP, materials hold great promise for wastewater treatment for removal of metal ions and complexes. A series of TiP materials, synthesised at mild conditions and short reaction times, have been structurally characterised using solid-state X-ray absorption spectroscopy, phosphorus and titanium K edge XANES and EXAFS, and 31P and 47/49Ti NMR spectroscopy. The titanium K edge EXAFS data of α-Ti(HPO4)2·H2O (α-TiP) revealed octahedral coordination of oxygens around titanium. Repeated washing of primary β-/γ-TiP with hydrochloric acid results in formation of a weakly ordered solid, TiO(OH)(H2PO4)·H2O, TiP1-H. The structure of TiP1-H is shown by Ti EXAFS to be a titanyl compound, containing a short Ti[double bond, length as m-dash]O bond. The analogous data for linked titanium phosphate compounds (LTP) disclosed that inter-linkage occurs between α-TiP and titanyl phosphate units, supported by 31P–31P NOESY NMR data. 47/49Ti NMR and Ti pre-edge XANES show evidence of two different titanium environments in LTP, one very similar to that observed in TiP1-H and a second more symmetric octahedral environment. Data are discussed in terms of induced acidic hydrolyses of titanium(IV) and phosphate counterpart during washings with hydrochloric acid and water. A straightforward relation between synthesis parameters/post synthetic treatment and structural re-arrangement in the materials is established.

Graphical abstract: Synthesis and structural characterisation of solid titanium(iv) phosphate materials by means of X-ray absorption and NMR spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
24 Mar 2022
Accepted
08 May 2022
First published
09 May 2022
This article is Open Access
Creative Commons BY license

Dalton Trans., 2022,51, 8192-8207

Synthesis and structural characterisation of solid titanium(IV) phosphate materials by means of X-ray absorption and NMR spectroscopy

D. Rusanova-Naydenova, M. Trublet, W. Klysubun, C. Cholsuk, D. Iuga, R. Dupree, O. N. Antzutkin and I. Persson, Dalton Trans., 2022, 51, 8192 DOI: 10.1039/D2DT00902A

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