Question: What are molecular sieves?

Rowena Fletcher-Wood answered on 14 Mar 2014:

Molecular sieves are three dimensional solid materials filled with pore channels like a giant hard sponge. They often have water or metal ions in the pores which give them their chemistry. My frameworks are negatively charged because they consist of alimunium and silicon atoms “joining hands and feet” at oxygen atoms to make a framework with a -1 charge per aluminium. This is made neutral by sodium ions in the pores.

Different sized pores let different sized moleviles through or trap them on their way. Molecular sieves are used for making high oxygen air for use in hospitals, taking up pollutants and cat litter!