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Based on the density functional theory(DFT)calculations,we showed that the interactions between different valence anions(PO43-,CH3PO4,(CH3)2PO4)and graphene significantly increased as the valence of anion increased from nega-tive monovalence to negative trivalence.The adsorption energy of(CH3)2PO4 on the electron-rich graphene flake(C84H24)is-8.3 kcal/mol.The adsorption energy of CH3PO4 on the electron-rich graphene flake(C84H24)is-48.0 kcal/mol,which is about six times that of(CH3)2PO4 adsorption on electron-rich graphene flake(C84H24)and is even much larger than that of CO3 adsorption on electron-deficient aromatic ring C6F6(-28.4 kcal/mol).The adsorption energy of PO4 on the electron-rich graphene flake(C84H24)is-159.2 kcal/mol,which is about 20 times that of(CH3)2PO4 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 π-electron-rich carbon-based nanomaterials and is helpful for the design of graphene-based DNA biosensor.