Introduction of targeted defects into microporous UiO-66s for manipulating their three-dimensional size and surface properties can endow them with adsorption and separation areas involving angiotensin-converting-enzyme-inhibitory (ACE-inhibitory) peptides. Three hydrophobic amino acids (AAs) (i.e., proline (Pro), phenylalanine (Phe), and tryptophan (Trp)) having different physical/chemical properties were applied to in situ tailor defects in UiO-66 through targeted incoordination of missing linkers or missing nodes. Characterization results revealed a uniform oval shape of the developed defects with lengths ranging from 1.8 to 3.1 nm, which was also highly consistent with our molecular simulation. Among these three defective UiO-66s, Phe and Trp imprinted UiO-66s significantly promoted the adsorption affinity of small ACE-inhibitory peptides (uptake: 1.25 mmol g-1 for DDFF and 1.37 mmol g-1 for DDWW) and ultrahigh selectivity for DDFF (249) or DDWW (279) from inactive KKKK solution based on a lock-and-key mechanism. As a result, the imprinted UiO-66 showed an enrichment capacity for ACE-inhibitory peptides about eight times higher than that of pristine UiO-66. Therefore, the amino acid imprinting strategy endorsed by its facile and discerning ability can be envisioned to be of great value for small functional peptide separation and oriented enrichment in biomedicines.
Keywords: ACE-inhibitory peptides; amino acid imprinting; defective UiO-66; oriented enrichment; recognized adsorption; separation.