A Comparative Study to understand the potential of DES [ChCl-PD] towards HCN binding

Hydrogen cyanide (HCN) gas, a major industrial pollution, is generated as a result of burning fossil fuels and indirectly contributes to the greenhouse effect. Therefore, deep eutectic solvents (DES) can provide a low-cost and effective method for its detection and removal. Density function theory (DFT) computations have been used to conduct a theoretical investigation of a DES, composed of choline chloride (ChCl) and 1,3-propanediol (PD). The potential of DES for HCN adsorption or binding has been examined using computational calculations. Herein, the viability of adsorption of HCN by the DES composed of ChCl and PD in 1:1 and 1:2 ratio, that is, 2a and 3a have been studied and further, the number of HCN molecules have been varied. The study was conducted by analysing the interactions and electronic properties obtained from DFT computations. Density of states (DOS) spectra were determined and used to examine the stability of the complex formed between DES and HCN. Significant interactions between DES systems and HCN molecules have been observed. Natural bond orbital (NBO) analysis indicated an increase in the strength of interactions upon an increase in PD molecules. Molecular dynamics (MD) simulations of the DESs with and without HCN were performed and investigated. Root mean square deviation (RMSD) and root mean square fluctuation (RMSF) trajectories were extracted and used to analyse the interactions in DES and HCN at different ratios. The RMSD plots showed increased values with lower fluctuations with an increase in the number of HCN molecules, demonstrating that the structures remained in equilibrium despite the rise in the number of HCN molecules. RMSD patterns revealed the stability of the complex formed between DES and HCN molecules. RMSF plot indicated the stable geometries obtained upon interacting DES with HCN molecules. The number of hydrogen bonds increased with an increase in the number of DES molecules.