Grafting Going Green: Toward a Sustainable Preparation of Organic–Inorganic Hybrid Materials

Abstract

Organic–inorganic hybrid materials find many applications in catalysis, nanotechnology, electronics, and many others. Grafting organic functionalities on inorganic supports is one of the most used methods for their preparation. Toluene is the solvent of choice for the grafting reaction, but it is fossil fuel-derived and not devoid of toxic effects. In this work, we explore the use of sustainable alternatives, i.e. , (+)-α-pinene, (−)-β-pinene, dimethyl carbonate (DMC), (+)-limonene, and 2-methyl-tetrahydrofuran (MeTHF), as solvents for grafting. The grafting reaction between 3-aminopropyltriethoxysilane (APTS) and mesoporous ordered silica (MCM-41) was selected as a model for this study. A comparison of the rate of the grafting reaction in different solvents is reported. The resulting hybrid materials were analyzed by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) and compared to the reference material prepared in toluene. MeTHF proved to be the best sustainable alternative to toluene for model grafting, providing a comparable product in a significantly shorter reaction time.

Hybrid Materials: A Metareview

“…In this sense, sol–gel synthesis, developed in 1930s, has become one of the major research lines in the broad field of hybrid materials synthesis. ,,− Organic molecules or monomers embedded in sol–gel matrices are common examples that could present a large diversity in their structures and final properties leading to many multifunctional materials. Polymers filled with inorganic clusters, organogels, and biological-based hybrid materials are other extended examples of class I hybrids. ,,,,,,− ,− In the case of Class II hybrid materials, covalent or ion-covalent bonds are present between the organic and inorganic phases. , In this sense, the grafting methodology, appears as a common strategy to form class II hybrid materials. ,,,,,,− This method, sometimes applied as a postsynthetic step, normally implies the attachment of functional organic molecules on the surface of inorganic moieties (type I–O), such as silica, titania, other metal oxides, and/or carbon surfaces. ,,, Sol–gel is again one of the most used as a suitable methodology for the preparation of this class of materials, with the development of hybrid materials from polyfunctional alkoxysilanes a typical example for obtaining a wide range of functional materials due to their high versatility. − However, electrochemical grafting using aryl diazonium salts is the most used in the case of carbonaceous matrices. This method is based on the electrochemical reduction of diazonium salts, which decompose into radicals and nitrogen gas, giving a direct C–C bond. , Other typical methods commonly used to prepare type II hybrid materials are self-assembly synthesis, ,, template-assisted synthesis, ,, hydrothermal, ,,,…”

“… 20 , 46 In this sense, the grafting methodology, appears as a common strategy to form class II hybrid materials. 13 , 14 , 43 , 44 , 53 , 58 , 61 − 64 This method, sometimes applied as a postsynthetic step, normally implies the attachment of functional organic molecules on the surface of inorganic moieties (type I–O), such as silica, titania, other metal oxides, and/or carbon surfaces. 3 , 23 , 65 , 66 Sol–gel is again one of the most used as a suitable methodology for the preparation of this class of materials, with the development of hybrid materials from polyfunctional alkoxysilanes a typical example for obtaining a wide range of functional materials due to their high versatility.…”

Application of Mesoporous Carbon-Based Highly Dispersed K–O2 Strong Lewis Base in the Efficient Catalysis of Methanol and Ethylene Carbonate

“…However, this reaction often requires high temperatures and pressures, and HCl produced via the deactivation of the used catalyst (e.g., CuCl) is extremely corrosive to equipment . In contrast, as an atom-economical reaction, the direct generation of DMC and ethylene glycol (EG) via the transesterification of CH 3 OH and ethylene carbonate (EC) has several promising applications. , The coproduced products, i.e., DMC and EG, can be used to prepare higher-value chemicals, e.g., polycarbonate (PC) and polyethylene glycol (PEG), and in a broad range of applications (e.g., various organic reactions and additives). − These chemicals can also be utilized in the healthcare sector. For instance, DMC is used as a pharmaceutical intermediate in the production of antibiotics, anticancer drugs, and anesthetics, , and EG is used as a solvent and a stabilizer for many oral and topical drugs .…”