One-step nonhydrolytic sol–gel synthesis of mesoporous TiO₂ phosphonate hybrid materials

Abstract

Mesoporous TiO2–octylphosphonate hybrid materials were prepared in one step by a nonhydrolytic sol–gel method involving the reaction of Ti(OiPr)4, acetophenone (2 equiv) and diethyl octylphosphonate (from 0 to 0.2 equiv) at 200 °C for 12 hours, in toluene. The different samples were characterized by 31P magic angle spinning nuclear magnetic resonance, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and nitrogen physisorption. For P/Ti ratios up to 0.1, the hybrid materials can be described as aggregated, roughly spherical, crystalline anatase nanoparticles grafted by octylphosphonate groups via Ti–O–P bonds. The crystallite size decreases with the P/Ti ratio, leading to an increase of the specific surface area and a decrease of the pore size of the hybrid samples. For a P/Ti ratio of 0.2, the volume fraction of organic octyl groups exceeds 50%. The hybrid material becomes nonporous and can be described as amorphous TiO2 clusters modified by octylphosphonate units, where the octyl chains form an organic continuous matrix.

Water-Stable, Nonsiliceous Hybrid Materials with Tunable Porosity and Functionality: Bridged Titania-Bisphosphonates

“…37 Recently, we used a nonhydrolytic route involving the reaction of titanium isopropoxide, acetophenone and diethyl octylphosphonate to prepare mesoporous titania-phosphonate hybrids, but the octylphosphonate groups prevented the growth of titania domains; as a result, the pore volume was moderate and decreased rapidly when increasing P/Ti ratio. 38 Here we show that the key to high pore volumes is to combine nonhydrolytic sol−gel with rigid bis-diethylphosphonate precursors. In this case, the growth of TiO 2 is not prevented and the final material is built of anatase nanorods cross-linked by fully condensed bridging bisphosphonates.…”

“…Nonhydrolytic sol–gel, which offers much more manageable rates, can provide an elegant solution to this problem . Recently, we used a nonhydrolytic route involving the reaction of titanium isopropoxide, acetophenone and diethyl octylphosphonate to prepare mesoporous titania-phosphonate hybrids, but the octylphosphonate groups prevented the growth of titania domains; as a result, the pore volume was moderate and decreased rapidly when increasing P/Ti ratio …”

Hybrid porous titania phosphonate networks with different bridging functionalities: Synthesis, characterization, and evaluation as efficient solvent separation materials

“…The TiO2-C3-3 material reaches the highest SBET of 379 sm 2 /g, which is lower than found for the recently presented hybrid materials from diphosphonate esters showing SBET values up to 830 m 2 /g [29]. The TiO2-C8 materials however display higher surface areas compared to hybrid titania prepared nonhydrolytically with diethyloctylphosphonate esters (10 -240 m 2 /g) described in literature [54].…”

Advanced hybrid nanomaterials

“…A one-step non-hydrolytic sol-gel synthesis of mesoporous TiO 2 phosphonate hybrid materials was applied to yield diverse materials, which were found to depend on the P/Ti atom ratio [20]. The ratio was found to determine the particle size and the aggregation state and thereby could strongly tune the porosity of the resulting materials.…”