Catenane Hosts for Solid Lithium Chloride Extraction: Selectivity Reversal, Binding Strength and Uptake Kinetic Enhancement via Post-Interlocking Modification

A strong and selective Li+-binding catenane host, featuring preorganized pyridine N-oxide binding motifs, was developed via the post-interlocking modification of catenane obtained from efficient transition metal templated synthesis. Not only the hard N-oxide catenane is selective against soft metals such as Cu+ and Ag+, but also the restrictive coordination empowers the large K+ and Na+ to remain unsaturated inside the interlocked cavity to result in a good Li+ selectivity. In addition, the post-modification also enhanced the Li+-binding strength, as well as the binding kinetics, which was demonstrated to be an essential parameter in practical LiCl extraction.