Because of the adsorption selectivity of different molecules from gaseous and liquid media, boron nitride (BN) nanostructures with large specific surface area are considered as useful materials in environmental protection, e.g., in water treatment for removal of organic pollutants. Here, we propose a theoretical model explaining the selectivity of boron nitride surfaces to adsorb different molecules. The weakness of interaction between BN hexagonal layers gives the possibility for such kind of reconstruction of the surface layer when B and N atoms are displaced in opposite directions from the surface plane. Bonding in BN is partially ionic, i.e., B and N atoms possess non-zero effective electrical charges of opposite signs. Thus, BN surfaces should be polarized and interact with ions, and induce and/or attract the electrical dipoles of molecules. The adsorption depends on the relation between electrical attraction and Pauli repulsion forces between BN hexagonal surface and molecules, i.e., their characteristics, such as size, charge, dipole moment, and polarizability.