Pyrene-based covalent organic framework for selective enrichment of hydrophobic peptides with simultaneous proteins exclusion

Owing to the desirable structures, covalent organic frameworks (COFs) have emerged as promising porous crystalline materials in bioanalytical and biomedical science. However, the application of their merits for analysis of hydrophobic peptides in complicated bio-samples has not been well investigated, possibly due to challenges in developing materials with high-specific binding effect of target peptides and accurate controllable pore-size for high selectivity. In this study, we proposed the size-exclusive peptide enrichment with Azo-COF constructed from 1,3,6,8-tetrabromopyrene (TBPy) building block and p-azoaniline linking units. The as-synthesized sieve-like COFs show high surface area together with accessible nanometer pore size (∼2.5 nm). With these advantages, specific enrichment of hydrophobic peptides using Azo-COF can be achieved by simply packing them in a 100 μL Axygen pipette tip. A maximum capacity of 36 mg g^-1 for FGFGF was obtained, which is more than a magnitude order larger than those of hydrophilic peptides. Furthermore, this method was successfully applied in analysis of hydrophobic peptides in tryptic digest of proteins and real human serum samples, indicating that the proposed method is promising for high-selective peptides enrichment from complex biological samples, and is of great value for further application of the functional materials in bioanalysis.