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Calculations based on second-order Moller-Plesset and density functional theory (DFT) methods using different exchange and correlation functionals are performed on C 2 H 4 Nb organometallic complex for its hydrogen storage capacity. We found that this complex can store up to a maximum of 14 H 2 molecules using Becke-3 Lee-Yang-Parr (B3LYP)/LanL2DZ method, with a gravimetric H 2 uptake capacity of 18.92 wt% and average binding energy of 0.52 eV/H 2 . The evaluation of the temperature dependence of the Gibbs free energy change (DG) of H 2 adsorption process indicates that the adsorption of H 2 molecules is energetically favorable below 250 K using B3LYP (LanL2DZ) and PBEPBE (LanL2MB, LanL2DZ) level of theories. On the basis of the DFT descriptors, calculated at B3LYP (LanL2DZ) and B3PW91 (LanL2MB) level of theory, we found that the stability of the complex increases with increase in the number of H 2 molecules adsorbed by the complex.

Microwave−ultrasound-assisted facile synthesis of a dumbbell-and flowershaped potato starch phosphate (PSP) polymer, hereafter PSP, was carried out by crosslinking the hydroxyl groups of native potato starch (NPS) using phosphoryl chloride as a cross-linking agent. Structural and morphological analysis manifested the successful formation of the dumbbell-and flower-shaped PSP biosorbent with enhanced specific surface area and thermal stability. Viscoelastic behavior of NPS and PSP suggested increased rigidity in PSP, which helped the material to store more deformation energy in an elastic manner. The synthesized PSP biosorbent material was successfully tested for efficient and quick uptake of Zn(II), Pb(II), Cd(II), and Hg(II) ions from aqueous medium under competitive and noncompetitive batch conditions with q m values of 130.54, 106.25, 91.84, and 51.38 mg g −1 , respectively. The adsorption selectivity was in consonance with Pearson's hard and soft acids and bases (HSAB) theory in addition to their order of hydrated radius. Adsorption of Zn(II), Pb(II), Cd(II), and Hg(II) followed a second-order kinetics and the adsorption data fitted well with the Langmuir isotherm model. Quantum computations using density functional theory (DFT) further supported the experimental adsorption selectivity, Zn(II) > Pb(II) > Cd(II) > Hg(II), in terms of metal−oxygen binding energy measurements. What was more intriguing about PSP was its reusability over multiple adsorption cycles by treating the metal(II)-complexed PSP with 0.1 M HCl without any appreciable loss of its adsorption capacity.

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