Magnetic mesoporous carbon nanocomposites derived from bimetallic metal–organic frameworks for enrichment of low-abundance peptides†

Mesopore-structured cobalt and nickel metal–organic frameworks (Co/Ni-ZIF) were synthesized by a self-assembly method using Co and Ni as bimetallic centers and 2-methylimidazole as the organic ligand at room temperature. The resulting rhombic dodecahedral nanocomposites possessing rich mesopores with an average diameter of 4 nm were collected centrifugally and then carbonized under a nitrogen atmosphere to generate bimetallic magnetic porous carbon nanocomposites (Co/Ni-MCNs). After thorough characterization, the as-prepared Co/Ni-MCNs decorated with a graphite shell layer with pyridinic nitrogen were utilized in magnetic separation and enrichment of low-abundance peptides through hydrophobic and π–π stacking interactions. This is the first attempt to prepare mesoporous carbon materials having plentiful holes with bimetal MOFs as precursors, in which partial nickel-containing components served as sacrificial templates. Owing to the ordered structure, abundant mesopores, rich interaction sites, excellent magnetic properties and good compatibility with biological tissues, this proposed magnetic affinity probe has been successfully used in the identification of endogenous peptides in human urine and serum in combination with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS).