Zeolites as Green Catalysts for Organic Synthesis: the Cases of H-, Cu- & Sc-Zeolites

Within the Green Chemistry context, one of the major challenges is the replacement of conventional homogeneous catalysts by heterogeneous catalysts, which are easy to handle and usually recyclable since they can be readily recovered. This paradigm change is becoming particularly significant with the development of zeolites, either in their native acidic form or modified by metal ions, as catalysts in organic chemistry. Due to the current burgeoning of this new field, the present review only covers some typical but representative aspects. Typical reactions of carbohydrates and other acid-sensitive organic compounds can be catalyzed by H-zeolites, advantageously replacing dangerous and toxic strong acids. Metal-doped zeolites can act as catalysts for various transformations. Some cycloadditions, including the well-known 'click' reaction, and coupling, specially Cu-catalyzed reactions. This new kind of heterogeneous catalysts can be recycled and reused, in sharp contrast to conventional homogeneous catalysts.