Influences of hydrogen bonding dynamics on adsorption of ethyl mercaptan onto functionalized activated carbons: A DFT/TDDFT study

• The intermolecular hydrogen bonding dynamics in the adsorption process has been first investigated in detail.
• In the ground state, the trend of hydrogen bonding interactions facilitating adsorption is I > II and III > IV.
• In the excited states, the hydrogen bond interactions of complexes I, II and III can facilitate adsorption, while that in complex IV is against adsorption.
• The photoexcitation for complex IV should be controlled during the absorption process.

The intermolecular hydrogen bonding dynamics between the functionalized activated carbons (AC) and ethyl mercaptan (ETM) were investigated using DFT and TDDFT methods, respectively. The ground-state and excited-state structures, electronic excitation energies and corresponding oscillation strengths of the low-lying electronically excited states for the functionalized ACs and their hydrogen-bonded complexes I, II, III and IV were calculated. It is demonstrated that the stability trend of forming hydrogen-bonded complexes is I > II and III > IV, which coincides with the results from the interaction energies calculation EHB. Moreover, according to Zhao's rule on the excited hydrogen bonding dynamics, it is found that the hydrogen bonds in the complexes I, II and III are significantly strengthened, with the excitation energy of a related excited state being red shifted, the hydrogen bond interactions can facilitate ETM adsorption onto AC-COOCO, AC-CCC and AC-CO, respectively. The intermolecular hydrogen bond of complex IV in the excited state is noteworthily weakened, in which the excitation energy of a related excited state is blue shifted. Therefore, the hydrogen bond interaction in complex IV is against ETM adsorption onto AC-OH in the excited state. The photoexcitation for complex IV should be controlled during the absorption process.