Beyond TS-1: Background and recent advances in the synthesis of Ti-containing zeolites

The discovery of Titanium-Silicalite-1 (TS-1), reported in the late 1970s, is a milestone in the science and technology of zeolites. As an oxidation catalyst, TS-1 operates under mild conditions with high activity and selectivity, and it is presently applied in several industrial processes. As a medium-pore zeolite, the small size of the 10-ring pore openings imposes diffusion limitations when working with even relatively large molecules. To overcome this drawback, a thriving line of research was soon undertaken aimed at incorporating Ti into the framework of zeolites with different pore architecture and sizes. In this review, we would like to retrace the fundamental steps of the synthesis of crystalline microporous titanosilicates, highlighting not only the early works but, above all, the most recent advances. The analysis of the literature provides an exhaustive picture of the efforts made by the researchers together with useful indications for developing increasingly selective and efficient catalytic materials.