Catalysis by Sol-Gels: An Advanced Technology for Organic Chemistry

Catalysis by sol-gel doped materials -- chemical conversions mediated by porous glassy matrices containing actives entrapped within their internal huge porosity -- is now a developed chemical technology offering unique advantages in terms of catalyst stability, selective activity and versatility which include ease of materials production and application. In general, the performance of these materials is largely superior compared to other catalytic solids obtained by traditional support impregnation methods, while they offer entirely new possibilities prior unavailable in catalysis. Selective activities higher than in solution; mutually destructive catalysts in one pot; fast conversions in carbon dioxide; smooth reactions in water with hydrophobic catalysts; entrapped enzymes 10 times more active than in solution; asymmetric syntheses with full recovery of the precious catalyst: These are just a few examples of the chemical wonders made possible by these materials. The reactivity of sol-gel catalysts can indeed be controlled and tailored to meet the requirements of largely different chemical conversions either by varying their structural properties (surface polarity, porosity, surface area, morphology etc.) or even the chemical activity of the encapsulated active. The technology is being increasingly adopted by industry while intense researches are carried out worldwide in several academy and industry laboratories. In order therefore to prevent its rapid obsolescence, this review intends to outline the general findings emerging from research on catalysis by sol-gels to help the reader organic chemist in adopting a sol-gel catalyst as a viable and practical tool to achieve the desired products.