Abstract: A molecular sieve, which contains in all, or only in some, of its cavities colorant molecules as well as a modifier which is covalently bound to said molecular sieve and which reduces its pore diameter, a process for its preparation as well as its use as pigment for coloring high molecular weight organic materials, preferably biopolymers and plastic materials, glasses, ceramic products, for formulations of decorative cosmetics, for the preparation of paint systems, preferably automotive lacquers, printing inks, dispersion paints and color filters as well as materials comprising the novel molecular sieves.