Three molecules of 5-(bromoacetyl)salicylate (1) complexed to uranyl (UO22+) ion were crosslinked with branchy poly(ethylenimine) (PEI) in DMSO by alkylation of amino groups of PEI with 1, leading to the formation of UO2(Sal)(3)(PEI)-P-U. Upon demetalation of UO2(Sal)(3)(PEI)-P-U with HCl, apo(Sal)(3)(PEI)-P-U was obtained. Based on the pH dependence of log K-f for UO2(Sal)(3)(PEI)-P-U, it was concluded that each uranyl binding site in UO2(Sal)(3)(PEI)-P-U or apo(Sal)(3)(PEI)-P-U contains three salicylate moieties. In terms of the equilibrium constant for formation of the uranyl complex, apo(Sal)(3)(PEI)-P-U was found to be comparable to or better than the previously reported effective uranophiles. In terms of the rates for the formation of the uranyl complex, however, apo(Sal)(3)(PEI)-P-U was far superior to those other uranophiles.