Molecular modeling of nitrosamines adsorbed on H-ZSM-5 zeolite: an ONIOM study.

Binding energies of nitrosamine compounds, N-nitrosamine (NA), N-methyl-N-nitrososamine (NMA), N-ethyl-N-nitrososamine (NEA), N,N-dimethyl-N-nitrosoamine (NDMA), N-ethyl-N-methyl-N-nitrosoamine (NEMA) and N,N-diethyl-N-nitrosoamine (NDEA) on the H-ZSM-5 zeolite were obtained using the ONIOM(B3LYP/6-31G(d):AM1) approach. Based on amino and imino isomers of nitrosamines, there are two adsorption configurations on the H-ZSM-5 for NA (as NA_a and NA_i), NMA (as NMA_a and NMA_i) and NEA (as NEA_a and NEA_i). The relative binding energies of nitrosamines are in order: NA_a > NMA_a approximately NEA_a > NA_i > NMA_i approximately NEA_i > NEMA approximately NDEA > NDMA. The order of adsorption selectivity for nitrosamines of the H-ZSM-5 is NA_a approximately NA_i >> NMA_a approximately NEA_a > NDMA approximately NMA_i approximately NEMA > NDEA approximately NEA_i. The selective recognition of the NA by the H-ZSM-5 was obviously found.