The response of boron nitride nanosheets (BNNSs), with the chemical composition of B25N25H20, serving as an adsorbent of toxic hydrogen cyanide (HCN) is explored by using density functional theory (M06-2X variant of DFT). Atoms were treated with a triple-zeta quality basis set with p- and d-polarized functions, namely 6-311G(d,p). The primary focus of this study is to explore adsorption properties (adsorption energies and structures and interaction types) by introducing a single dopant (C/Si or Al) atom, by substituting either B or N at the center of the BNNS. Also considered is the effect of charge modulation on the neutral pristine and doped BNNS-HCN systems by inserting and extracting an electron. Adsorption energy varied in the range from 2.9 to 71.5 kcal/mol. The source of interactions between adsorbent and adsorbate varies from weak H-bonding to strong N→ B dative bond formation. Removal of an electron from C- or Si-doped BNNS-HCN binds both units more tightly (25.8 to 49.5 kcal/mol) than in their neutral form (2.8-6.2 kcal/mol). Thus, storage of HCN is possible by removing an electron from the neutral complexes and desorption or releasing process (to reuse captured HCN) may be easier by adding an electron to the cationic forms. The most striking feature evolved by doping and charge modulation is the cleavage of the H-CN bond in the reduced form of C-BNNS-HCN complex, where B is replaced by the C atom and a product-end transition state was identified. Electron-correlation MP2 method with 6-31G(d) basis set confirmed DFT prediction of such Hsingle bondC activation. In Al-doped BNNS-HCN, dative (HC)-N → Al(BNNS) bond formation in most of the complexes (neutral, as well as charged) is quite stable (20 to 33 kcal/mol) which would inhibit release of HCN from Al-doped BNNS. Overall charge modulation can make doped BNNSs an excellent adsorbent with different characteristics and several uncommon and unusual but useful features evolved from this study.
