Adsorptive capacity of a g-C3N4 matrix for thiamethoxam removal: A DFT study

• The g-C 3 N 4 matrix was studied to evaluate the adsorption capacity of the thiamethoxam (TMX). • The interaction of the TMX contaminant with the g-C 3 N 4 matrix occurs through of hydrogen bonds. • Binding energies (ΔE Bind ) showed that the interaction is effective and with value of ≅ -70 kJ mol −1 . • The adsorption of TMX with the g-C 3 N 4 matrix was spontaneous (Δ r G < 0) and exothermic (Δ r H < 0) by DFT studies. In this study, the adsorptive capacity of the insecticide thiamethoxam (TMX) on a graphitic carbon nitride matrix (g-C 3 N 4 ) was studied theoretically. Two adsorbent-adsorbate complexes, g-C 3 N 4 -TMX 1 and g-C 3 N 4 -TMX 2 was formed through hydrogen bonds (HB) and the the hydrogen bonds lengths ranging from 2.610 Å to 3.538 Å. Topological analyses based on the quantum theory of atoms in molecules confirmed the bond critical points of hydrogen bonds. Further, it allowed for the classification of the HBs as weak, with hydrogen bond energy values ranging from −0.98 to −6.58 kJ mol −1 . Calculations of the energies involved in the processes proved that the interaction of TMX with the g-C 3 N 4 matrix occurs in two sites with values of ΔE Bind = −71.65 kJ mol −1 and ΔE Bind = −70.44 kJ mol −1 , sites 1 and 2, respectively. The results showed that the interaction is is spontaneous and exothermic, as indicated by the negative values of ΔG and ΔH.