Efficient capture of Pd by multidentate S/N-containing group modified materials: An important piece of puzzle for electron transfer ratio ligand design

Abstract

How to quantitatively describe metal–ligand interactions is the key to design high-affinity ligand. In this study, the electron transfer ratio (ETR), which correlated 34 chemical ligands with the electron donating ability, allowed for obtaining six high affinity multidentate S/N-containing ligands, and the interactions were further analyzed by frontier orbital and electrostatic potential calculation. Furthermore, six corresponding ligand-modified polystyrene framework materials were prepared by efficient derivatization of isothiocyanates and primary amines. The optimal material CMPS-BD had an adsorption capacity up to 4.07 mmol/g with good tolerance to different organic solvents. CMPS-BD exhibited excellent adsorption efficiency in combination with kinetics, thermodynamics, selectivity and regeneration performance. Moreover, the remarkable practicability was achieved as the removal rate reached 99.8 %, and the residual Pd2+ concentrations were reduced to less than 5 mg/L in three kinds of Pd-catalytic reaction waste liquids. Through mechanism analysis, 1 mmol ligand FA ∼ BD could bind 0.75 ∼ 1.74 mmol Pd2+ which was consistent with the ETR tendency, certifying the accuracy and efficiency of this method. Intensive DFT calculations revealed that the optimal ligand BD could generate a variety of spontaneous endothermic intermolecular and intramolecular coordination reactions.