Abstract
N-termini Cyano group (CN) in metal hexacyanoferrates (MHCF) have been identified as specific-affinity sites for palladium (Pd), but C-termini CN do not effectively serve as Pd adsorption sites due to their stronger bonds with the metal ligands (M), which reduces the activity and density of CN. Herein, the optimization of directional coordination of cyano group C/N-termini by modulating the electronic structure of the M (FeII, CoII, and NiII) in MHCF was investigated to reinforce the Pd recovery. Spectroscopic analyses and DFT calculations revealed that NiHCF exhibited N-site mono-coordination, whereas CoHCF displayed C-site mono-coordination due to spin-exchange interactions, leading to the strengthened N-CoIII bonds and weakened FeII-C bonds. Interestingly, FeHCF maintained N-coordination properties and showed C-coordination as the shift of the d-band center weakened the FeIII-C bonds. Double-coordination of CN resulted in a higher adsorption-capacity and -rate than mono-coordination, which were attributed to its greater CN content and adsorption affinity, respectively. Additionally, all three MHCFs, particularly double-coordination FeHCF, demonstrated excellent selectivity in noble/base metal systems, good resistance to anionic interference, and reusability. The study underscores the pivotal role of M's electronic structure in the CN coordination environment, offering a novel strategy for the directional design of adsorbent sites.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call