Search Engines for Shape Selectivity

Zeolites have been used successfully for over 30 years to separate small molecules of almost identical physical and chemical properties, relying on shape differences such as normal from branched paraffins. Many zeolites have approximately circular windows and these are the only ones used in current applications. As of today, the structures of 176 zeolites are available; many of them have windows that may be described as elliptic or irregular, presenting many opportunities for shape selective catalysis or adsorption. A molecule approaching a window may take a number of orientations, and it is difficult to visualize the three-dimensional shape and the best fit to the window. Search engines are needed to accelerate the discovery of one or more zeolite windows that can separate a given pair of molecules. A great deal of progress has already been made to construct such search engines, and innovative industrial processes may follow in the future.