Finally, destabilizing effects emerge at least 80% due to Pauli repulsion (EPAULI) in all the cases because the geometrical structure of As(III)/As(V) is weakly influenced upon non-covalent adsorption. A high EPAULI term appears in the As(V)-PhosO complexes due to the strong negative charge excesses in both the adsorbent and adsorbate (up to EPAULI14 eV, Table ). However, the magnitude of steric repulsion is lower than the main stabilizing forces (|EELEC+EPOL+ECT|>EPAULI), leading to stable adsorption. Conversely, in the highly-oxidized phosphorene nanoadsorbents [PhosO(1:2), PhosO(1:1)], the arsenic uptake comprises a large contribution of Pauli repulsion due to the high oxygen concentration on the adsorbent surface. Consequently, Pauli repulsion is overcompensating all the attractive forces (|EELEC+EPOL+ECT|<EPAULI), leading to the increase of the electron density kinetic energy when negatively charged fragments are brought into close interaction . The latter explains why highly oxidized phosphorene nanoadsorbents do not provide additional adsorption performance for arsenic removal than medium-oxidized phosphorene.