The present invention relates to polymeric structures, in the form of flat membrane-like surfaces or micro- nanostruc-tures such as capsules, characterized in that it comprises a substantially two-dimensional layer of covalently-bonded monomers of R-substituted metal or metalloid oxides. Said polymeric structures in most embodiments have a crystal architecture with a hexagonal lattice, but the nature of the covalent bonds present therein impart a bending flexibility that make the polymeric structures behave as a “soft” crystal. Methods of producing such structures, composition comprising thereof and method of using thereof are also included within the present disclosure.