Method for the selective bivalent binding of a natural or synthetic substrate, having at least two different groups capable of binding, to a sorbent, which comprises a solid carrier and at least two different groups capable of binding to the natural or synthetic substrate, wherein the method comprises the steps (i) to (iv): (i) determining at least two groups capable of binding a sorbent from the natural or synthetic substrate, (ia) binding an underivatised polymer via non-covalent interactions to the carrier, (ii) respectively introducing at least two different groups capable of binding the natural or synthetic substrate via at least two identical or different functional groups of the polymer into the polymer, thereby forming at least one sorbent, whereby the groups are groups that are complementary to the groups determined in step (i), whereby a derivatised polymer having at least two different groups capable of binding is formed, and the respective at least two different groups capable of binding are covalently bonded to the polymer, wherein (a) the groups are determined such that the contributions of the Gibbs energies of the individual groups for the non-covalent bond with the substrate results in a negative value of the Gibbs energy ΔG, so that a binding strengthening occurs, which results in an improved separation selectivity α, by way of which the substrate to be selectively bound having the at least two different groups capable of binding to the at least one sorbent is separated off from a substrate mixture by way of using the at least one sorbent, of more than 1.4 and wherein (iii) contacting the substrate with the sorbent of step (ii); (iv) testing the binding strength of the substrate to the sorbent of step (iii). (i) determining at least two groups capable of binding a sorbent from the natural or synthetic substrate, (ia) binding an underivatised polymer via non-covalent interactions to the carrier, (ii) respectively introducing at least two different groups capable of binding the natural or synthetic substrate via at least two identical or different functional groups of the polymer into the polymer, thereby forming at least one sorbent, whereby the groups are groups that are complementary to the groups determined in step (i), whereby a derivatised polymer having at least two different groups capable of binding is formed, and the respective at least two different groups capable of binding are covalently bonded to the polymer, wherein (a) the groups are determined such that the contributions of the Gibbs energies of the individual groups for the non-covalent bond with the substrate results in a negative value of the Gibbs energy ΔG, so that a binding strengthening occurs, which results in an improved separation selectivity α, by way of which the substrate to be selectively bound having the at least two different groups capable of binding to the at least one sorbent is separated off from a substrate mixture by way of using the at least one sorbent, of more than 1.4 and wherein (a) the groups are determined such that the contributions of the Gibbs energies of the individual groups for the non-covalent bond with the substrate results in a negative value of the Gibbs energy ΔG, so that a binding strengthening occurs, which results in an improved separation selectivity α, by way of which the substrate to be selectively bound having the at least two different groups capable of binding to the at least one sorbent is separated off from a substrate mixture by way of using the at least one sorbent, of more than 1.4 and wherein (iii) contacting the substrate with the sorbent of step (ii); (iv) testing the binding strength of the substrate to the sorbent of step (iii).