Reactivity Index Scale for Interaction of Heteroatomic Molecules with Zeolite Framework

Abstract

The activity of different interacting heteroatomic molecules such as CO2, CO, CH4, NO, NO2, NH3, and H2O along with the zeolite framework is investigated using a range of reactive indexes using density functional theory (DFT). From the values of the local softness and the charge on the hydrogen atom of the bridging hydroxyl, used as the first approximation to the local hardness, it is concluded that the acidities of the zeolite-type model systems, used in the calculations, are dependent on several characteristics which are of importance within the framework of the hard and soft acids and bases (HSAB) principle. We investigated the local softness of the interacting species, namely, CO2, CO, CH4, NO, NO2, NH3, and H2O, to compare their affinity with the zeolite framework cluster models. The recently proposed local hard−soft acid−base principle characterizes the reactive centers of two systems on the basis of equal local softness. We validate the proposition by considering the interaction between systems with different global softness, which further paves the way for proposing a novel qualitative scale “reactivity index” in comparing the activity of reactant species interacting with the zeolite framework. The results were compared with interaction energy calculations using DFT to validate the proposition. The result shows good agreement with the reactivity index scale for heterotomic molecules where the interaction is through the most nucleophilic atoms for CH4, CO2, CO, NH3, and H2O and the results differ for multisite interaction observed in the case of NO2 and NO. The proposed order of activity in terms of both methodologies is CH4 < CO2 < NH3 < H2O < CO.

Structure and dynamics of the water films confined between edges of pyrophyllite: A first principle study

“…The amphoteric "AlAOH and "AlAOH 2 sites inherit the properties of simple layered hydroxides (Churakov et al, 2004;Wang et al, 2004) or the octahedral surface of kaolinite (Warne et al, 2000;Tunega et al, 2004). The "AlAOASi" sites are common in zeolites (Chatterjee et al, 1999).…”

Application of Reactivity Indices Within Density Functional Theory to Rationale Chemical Interactions

“…Some DFT-based local properties, e.g. Fukui functions and local softness as reactivity index have already been used for the reliable predictions in various types of electrophilic and nucleophilic reactive species involving in the chemical reactions [67,68]. Moreover, the reactivity index scale can expand its domain successfully not only to predict the interaction between heteroatom and zeolite framework [69], but in various other fields [70][71][72][73][74][75].…”

Surface complexes of acetate on edge surfaces of 2:1 type phyllosilicate: Insights from density functional theory calculation

“…Quantum mechanical simulations have been widely employed to study surface complexes and proven very powerful in aiding both interpretation of experimental measurements and formulation of hypotheses (Chatterjee et al, 1999;Cygan, 2001;Sherman, 2001;Boek and Sprik, 2003;Aquino et al, 2004;Tunega et al, 2004;Bickmore et al, 2006;Boulet et al, 2006;Churakov, 2006Churakov, , 2007Aquino et al, 2007;Kubicki et al, 2007Kubicki et al, , 2008Michalkova and Tunega, 2007). Numerous simulations have focused on the bonding of inorganic oxyanions (e.g., arsenates, sulfates, phosphates and carbonates) on the surfaces of (hydr)oxides and have disclosed several probably stable complexation structures (Kubicki et al, 2007 and references therein).…”