Bioactive peptides, such as isoleucyl-tryptophan (IW), exhibit a high potential to inhibit the Angiotensin-converting enzyme. Adsorption on carbon materials provides a beneficial method to extract these specific molecules out of the complex mixture of an alpha-lactalbumin hydrolysate. This study focuses on the impact of nitrogen functionalization of porous carbon adsorbents, either via pre- or post-treatment, on the adsorption behavior of the ACE-inhibiting peptide IW and the essential amino acid tryptophan (W). The commercially activated carbon Norit ROX 0.8 is compared with a pre- and post-synthetically functionalized N-doped carbon in terms of surface area, pore size and surface functionality. For pre-functionalization a covalent triazine framework (CTF) was synthesized by a trimerization of an aromatic nitrile under ionothermal conditions. For the post-synthetic approach the activated carbon ROX 0.8 was functionalized with the nitrogen-rich molecule melamine. The batch adsorption results using model mixtures containing the single components IW and W could be transferred to a more complex mixture of an alpha-lactalbumin hydrolysate containing a huge number of various peptides. For this purpose reverse phase high pressure liquid chromatography (RP-HPLC) with fluorescence-detection was used for identification and quantification. The treatment with the three different carbon materials leads to an increase in the ACE-inhibiting effect in vitro. The modified surface structure of the carbon via pre- or post-treatment allows a separation of IW and W due to the certain selectivity for either the amino acid or the dipeptide.