Hybrid Inorganic−Organic Adsorbents Part 1: Synthesis and Characterization of Mesoporous Zirconium Titanate Frameworks Containing Coordinating Organic Functionalities

Abstract

A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd<100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and that of the other hybrid phases suggests that the surface-bound ATMP ligand functions as a chelating ligand toward 153Gd3+ under these acidic conditions.

Functionalized natural cellulose fibres for the recovery of uranium from seawater

“…It is hypothesized that both phosphonic acids become grafted to the bres through condensation reactions between the phosphonate groups and hydroxyl groups of the cellulose. Similar reactions are observed between organophosphonates and the hydroxylated surfaces of group (IV) metal oxides 29,30 and layered double hydroxides (LDH). The thermal and hydrothermal stability of glyphosate graed to the hydroxyl surfaces of LDH has been demonstrated at temperatures in excess of 180 C. 31 If it is the phosphonate group that gras to the cellulose surface then it must be the carboxylate groups of the glyphosate that bind uranium.…”

Sustainable synthesis of amino acids by catalytic fixation of molecular dinitrogen and carbon dioxide

“…In all cases, negative results were obtained demonstrating the importance of the 3-layered architecture, and thus discarding a process based on the photodecomposition of Phos. In addition, both the capability of incorporating water molecules 24 and the effective role of metal/phosphonate compounds as chelating ligands 25 are noteworthy due to the presence of free phosphonic acid groups. The results obtained after introducing the above-mentioned changes in the 3-layered p-HAp catalyst are summarized in Fig.…”

Phosphonate coupling molecules for the control of surface/interface properties and the synthesis of nanomaterials

“…Recent works suggest that the use of gem-bisphosphonate anchors can lead to particularly stable bonding to the surface, [104][105][106][107] although the size of the bisphosphonate limits the density of grafting. Furthermore, both phosphonate groups are not necessarily linked to the surface, 105,107 which may lead to the formation of multilayers.…”

“…Recent works suggest that the use of gem-bisphosphonate anchors can lead to particularly stable bonding to the surface, [104][105][106][107] although the size of the bisphosphonate limits the density of grafting. Furthermore, both phosphonate groups are not necessarily linked to the surface, 105,107 which may lead to the formation of multilayers. 108 SAMs of long-chain 1,1bisphosphonic acid on stainless steel were found to be stable for months in ultrapure water at 50 °C, and were not significantly degraded after 3 h in PBS solutions of pH 1-12.…”