Insight into the adsorption properties of CO2 and H2 gas on the B12Y12 (Y[dbnd]N, P, As, Sb) nanocages from host-guest interaction perspective

Abstract

Owing to the huge increase in population and industrial activity over the past century, the natural air environment is becoming increasingly polluted. Therefore, it is essential to monitor and regulate pollution levels. Numerous research efforts have been conducted to create acceptable gas-sensitive materials for continuing monitoring and sounding alarms when dangerous chemical vapors are present at higher than intended levels. In the theoretical analysis of the adsorption properties, density functional theory calculations were utilized for B12Y12 (YN, P, As, Sb) nanocages as gas sensor towards common air pollutants, CO2 and H2 molecules. In this study, the geometrical and electronic properties, highest occupied molecular orbital (HOMO) – lowest unoccupied molecular orbital (LUMO) energy gap, frontier molecular orbital (FMO) analysis were investigated. The shortest H2 and CO2 distances after the adsorption process were for B12N12 with distances less than 2.8 Å and 2.2 Å, respectively, and the adsorption energy when CO2 was adsorbed on the B12N12 surface was less than −26 kJ/mol, indicating that adsorption occurred physically and exorthemically. The Eg of B12N12 is 5.9 eV; therefore, compared to others, this nanocage is the most stable for H2 and CO2 adsorption. In addition, a positive ∇2ρ value and negative H value from the QTAIM analysis indicated the formation of moderate interaction between B12N12 and CO2. Density of states (DOS) and natural bond orbital (NBO) studies were performed to better understand the nanocage adsorption properties, which revealed the presence of physical interactions. Energy decomposition analysis was performed to investigate the stability of gas adsorption onto a nanocage surface. The results showed that ΔEDISP and ΔEELEC were significant factors in determining the adsorption process stability, and the adsorption type was physisorption based on ΔEPOL value for all nanocages. Molecular dynamics (AIMD simulation) analysis revealed changes in the bond lengths and angles during adsorption. This work provides the first theoretical framework for the carbon monoxide and hydrogen adsorption performance of B12Sb12 and B12As12.