The principle of molecular sieving molecules is based on the selectivity of their pore size. There are a large number of micropore channels and pore cages in the crystals of the molecular sieve with similar size to the molecular size. Only when the molecular dynamics diameter is smaller than the pore size of the molecular sieve can molecules enter the pore and be adsorbed. Molecules larger than the pore size cannot enter and can only pass through the pores, thereby achieving the purpose of separating molecules of different sizes.