Methanol and carbon monoxide sensing and capturing by pristine and Ca-decorated graphdiyne: A DFT-D2 study

Adsorption behavior of methanol and CO molecules on the pristine graphdiyne (GDY) and Ca-decorated graphdiyne (Ca-GDY) was investigated by modified density functional theory (DFT-D2) calculations. We examined center of 18-membered and hexagonal rings and top of the acetylenic chain, for pristine GDY and around the Ca atom for Ca-GDY. Three various orientations of methanol and CO molecules were investigated to find the best site and orientation for capture of these molecules. Results show that for pristine GDY and Ca-GDY, center of 18-membered ring and around the Ca atom are the best sites for methanol and CO capture, respectively. While, parallel orientation of methanol and C-head orientation of CO are more favorable directions. Also, E-ads values show that methanol and CO molecules (with E-ads of -0.349 and -0.128 eV, respectively) are physisorbed on the pristine GDY. But Ca-decorating remarkably increases the methanol adsorption ability up to similar to 4.15 and 5.63 times, respectively. We followed adsorption behavior of 1-6 molecules on one side and 1 to 12 molecules on both sides of Ca-GDY for CO and CH3OH molecules. It was seen that CH3OH and CO capture capacities of Ca-GDY are about 29.81 and 27.10 wt%, respectively.