▎ 摘　　要

Based on the density functional theory (DFT) calculations, we showed that the interactions between different valence anions (PO43-, CH3PO42-, (CH3)(2)PO4-) and graphene significantly increased as the valence of anion increased from negative monovalence to negative trivalence. The adsorption energy of (CH3)(2)PO4- on the electron-rich graphene flake (C84H24) is -8.3 kcal/mol. The adsorption energy of CH3PO42- on the electron-rich graphene flake (C84H24) is -48.0 kcal/mol, which is about six times that of (CH3)(2)PO4- adsorption on electron-rich graphene flake (C84H24) and is even much larger than that of CO32- adsorption on electron-deficient aromatic ring C6F6 (-28.4 kcal/mol). The adsorption energy of PO43- on the electron-rich graphene flake (C84H24) is -159.2 kcal/mol, which is about 20 times that of (CH3)(2)PO4- adsorption on the graphene flake (C84H24). The super-strong adsorption energy is mainly attributed to the orbital interactions between multivalent anions and graphene. This work provides new insights for understanding the interaction between multivalent anions and pi-electron-rich carbon-based nanomaterials and is helpful for the design of graphene-based DNA biosensor.