Constructing Biomimetic Nanochannels for High-Capacity Capture of Uranyl Tricarbonate Complex Ions

Biomimetic nanochannels enable fast and selective transport of mononuclear metal ions; however, their construction for complex ion transport remains in its infancy due to the nonuniform charge distribution and large geometric dimensions of coordination compounds. Herein, an ionic electrostatic interaction template strategy is proposed to prepare biomimetic channels for the capture of complex ions. Using the [UO₂(CO₃)₃]^4- ion as a template, various quaternary ammonium monomers with lengths of 6.2-8.4 Å are decorated on 1D porous channels of the TpBDOH framework via the Williamson ether reaction. Accordingly, the pore size is modulated in the sub-nanometer range of 9-13 Å, facilitating multiple electrostatic attractions between quaternary ammonium fragments and the three equatorial carbonate ions on the [UO₂(CO₃)₃]^4- ion. The unique structure enabled highly efficient uranium adsorption with a capacity of 501.5 mg g^-1 and a high selectivity coefficient for uranium over vanadium of >163.1. The resulting electropositive nanochannels selectively captured [UO₂(CO₃)₃]^4- ions from natural seawater, achieving a high uptake of 25.3 mg g^-1 in 35 days.