Quantum mechanical studies on dioxin-imprinted polymer precursor composites: Fundamental insights to enhance the...

We present a benchmark study of binding energies for dioxin-imprinted polymer complexes. A density functional theory approach was used for screening the polymerization precursors in the rational design of molecularly imprinted polymers (MIPs). Tetrachlorodibenzo-p-dioxin (TCDD) was taken as an imprinted molecule. The geometry optimization, natural bond orbital charge, and molecular electrostatic potential of TCDD and acrylamide (AM) were studied at the M062X level and 6-31G(d,p) belonging to one of the hybrid density functional theories. The results of molecular electrostatic potential and natural bond orbital charge analysis were comparable. Among the studied functional monomers-AM, methacrylic acid (MAA), itaconic acid, and vinyl pyridine-AM was confirmed as the best functional monomer, because the strongest interaction (the maximum number of hydrogen bonds and the lowest binding energy) occurs between TCDD and AM. The stability property was excellent when the ratio of TCDD and AM was 1:4. The polarizable continuum model was used for solvent calculations. Computational results showed that acetonitrile plays an important role in the MIP formation, as it seems to control the size and the shape of the cavity. The atoms in molecule and Becke surface method have also been applied to understand the nature and strength of the hydrogen bonding interactions in complexes. TCDD-AM complexes were found involving C-O···Cl and N-H···Cl hydrogen bonds. Good correlations have been established between hydrogen bond lengths versus atoms in molecule topological parameter like electron density ρ(r) and its Laplacian ▽² ρ(r) at the bond critical points. On ground of theoretical results, a series of MIPs were synthesized. The MIP prepared using TCDD as the template, the functional monomer (AM), and the cross-linker (TRIM) in acetonitrile solvent exhibited the highest adsorption capacity for TCDD. The maximum binding capacity of TCDD on the MIP was 3.7 μg/mg. This research work can provide a theoretical reference for the fabrication and characterization of novel TCDD-MIPs for environmental applications.