A nanoporous sorbent designed around chelating iminodiacetamide (“IDA-Amide”) moiety was made on mesoporous silica (MCM-41) and evaluated for lanthanide separations (Ce 3+ , Nd 3+ , Eu 3+ , Gd 3+ , and Lu 3+ ). The effects of solution pH on lanthanide binding were studied, as well as sorption kinetics, and competition from other metal ions. The IDA-Amide SAMMS® demonstrated an interesting difference in the kinetics of sorption of the lanthanide ions in the order of Lu 3+ >Eu 3+ >Gd 3+ >Nd 3+ >Ce 3+ . The close proximity of the ligands in the IDA-Amide SAMMS® may allow for multiple metal–ligand interactions (“macromolecular chelation”).