The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

Abstract

This review is devoted to non-hydrolytic sol-gel chemistry. During the last 25 years, non-hydrolytic sol-gel (NHSG) techniques were found to be attractive and versatile methods for the preparation of oxide materials. Compared to conventional hydrolytic approaches, the NHSG route allows reaction control at the atomic scale resulting in homogeneous and well defined products. Due to these features and the ability to design specific materials, the products of NHSG reactions have been used in many fields of application. The aim of this review is to present an overview of NHSG research in recent years with an emphasis on the syntheses of mixed oxides, silicates and phosphates. The first part of the review highlights well known condensation reactions with some deeper insights into their mechanism and also presents novel condensation reactions established in NHSG chemistry in recent years. In the second section we discuss porosity control and novel compositions of selected materials. In the last part, the applications of NHSG derived materials as heterogeneous catalysts and supports, luminescent materials and electrode materials in Li-ion batteries are described.

Acetic Anhydride as an Oxygen Donor in the Non‐Hydrolytic Sol–Gel Synthesis of Mesoporous TiO2 with High Electrochemical Lithium Storage Performances

“…The sol–gel process is the most common method used to synthesise mesoporous oxides because it offers the possibility to obtain metastable phases, with control over composition, homogeneity and texture. Conventional sol–gel chemistry based on hydrolysis and condensation reactions naturally predominates, but non‐hydrolytic (or non‐aqueous) sol–gel (NHSG) chemistry has been found to provide simple and powerful alternative routes notably for the synthesis of mixed oxides, nanoparticles and mesoporous materials …”

Controlled deposition of titanium oxide overcoats by non-hydrolytic sol gel for improved catalyst selectivity and stability

“…Non-hydrolytic sol-gel (NHSG) chemistry is a well-known technique for material synthesis and has been previously used for catalyst synthesis [28,29]. However, we have found limited use of sol-gel chemistry for the deposition of thin oxide films and its effect on catalysis.…”

“…Si CP ssNMR spectrum of pure SBA-15 (Fig. 3F) presented the 3 characteristic 29 Si resonances for bulk siloxanes (Q 4 ; @Si@; À111 ppm), silanols (Q 3 ; "SiOH; À100 ppm) and geminal silanols (Q 2 ; @Si(OH) 2 ; À90 ppm). After deposition of TiO 2 , the intensity of the Q 2 peak decreased due to the transformation of germinal silanols into silanols (@Si(OH)OTi) (Q 3 ), in agreement with 1 H NMR results.…”

Production of Nanostructured Aluminosilicate Fibers from Poly(ethylene glycol) Based Electrospun Fibers

“…Aluminosilicate NPs were produced by a typical sol‐gel method. GLYMO and ATSB underwent hydrolysis and condensation reactions catalyzed by HCl, forming a crosslinked three‐dimensional network without long‐range order . KCl was added to balance the charge.…”

“…These highly porous calcined inorganic fibers containing residual carbon may display favorable characteristics, such as high electrical conductivity and high‐surface area, to be used as a catalyst . Typically, small diameter fiber‐shaped soft templates and sol‐gel derived materials have high‐surface area owing to the empty spaces provided by the template. Moreover, silicate materials prepared by the sol‐gel process usually display high‐surface areas, since the hydrolysis and condensation reactions in acidic conditions of the alkoxides lead to the formation of small fractal polymerized entities or colloids that eventually will merge to form a highly porous material.…”