What is meant by ‘shape selective catalysis’?

Shape selective catalysis is defined as a catalytic reaction which depends upon the pore structure of the catalyst as well as on the size of the reactant and the product molecules.

One example of shape-selective catalysis is catalysis by zeolites. Zeolites are the aluminosilicates and are members of the family of microporous solids.

The pore size present in the zeolites ranges from 260-740 pm. Thus, molecules having a pore size more than this cannot enter the zeolite and undergo the reaction and small sized molecules are absorbed in the pores and cavities of zeolites.

Structure of zeolite.