In silico design of calixarene-based arsenic acid removal agents

Contamination of water resources with arsenic is a worldwide challenge with an important social impact. Development of adsorptive materials with high affinity and selectivity towards arsenic is an important and ongoing challenge. The aim of this work is to study calix[n]arenes with 4, 5, 6 and 8 rings, as well as COOH, C₂H₄OH, SO₃H, t-Bu, PO₃H₂ and PO₄H₂, upper-rim functional groups through computational chemistry models as tailor-made sequestering agents using pentavalent arsenate species (H₃AsO₄, H₂AsO₄ ⁻ and HAsO₄ ²⁻). Host–guest interaction energies (E_int) were determined using Density functional theory (DFT) calculations at the M06-2X/6-31G(d,p) level of theory carried out on host–guest adducts in order to find the most suitable candidates as extracting agents for these arsenate species. Hydrogen-bond donor groups such as SO₃H, PO₃H₂ and the hypothetical calixarene with R = PO₄H₂ on the upper rim of calix[n]arenes are shown to be the most suitable functional groups for encapsulating these As(V) species under study.