Natural sink of stratospheric ozone is

Natural sink of stratospheric ozone is Freons.
Freons is a registered trademark of the Chemours Company and generic descriptor for several halocarbon products. They are stable, nonflammable, low-toxicity gases or liquids which have generally been used as refrigerants and as aerosol propellants.
Freons are chlorofluorocarbon compounds that containcontain only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane and propane. These include the chlorofluorocarbons that cause ozone depletion and HCFCs.