Preparation of polyoxometalate modified magnetic metal–organic framework and application to the enrichment of phosphopeptides

Herein, polyoxometalate modified magnetic metal–organic framework (Fe3O4@PDA@MOF-POM) was successfully prepared and then applied to the enrichment of phosphopeptides. Fe3O4@PDA@MOF-POM can bind with phosphopeptides through ZrO clusters provided by the MOF layer and metal oxide originated from Zr-W-POM. The magnetic nanomaterial had high sensitivity (0.1 fmol), good reusability (10 cycles), and high selectivity (α-casein: β-casein: bovine serum albumin = 1: 1: 5000). Coupling with MALDI-TOF MS determination, non-fat milk was selected to preliminarily explore the applicability of Fe3O4@PDA@MOF-POM. Furthermore, 241 phosphopeptides derived from 232 phosphoproteins and 99 phosphopeptides attributed to 89 phosphoproteins were identified in human serum and saliva by nano LC-MS. This work paves a new way for the recognition of phosphopeptides in bio-samples.