[ThB5O6(OH)6][BO(OH)2]·2.5H2O (Notre Dame Thorium Borate-1, NDTB-1) is an inorganic supertetrahedral cationic framework material that is derived from boric acid flux reactions. NDTB-1 exhibits facile single crystal to single crystal anion exchange with a variety of common anions such as Cl−, Br−, NO3−, IO3−, ClO4−, MnO4−, and CrO42−. More importantly, NDTB-1 is selective for the removal of TcO4− from nuclear waste streams even though there are large excesses of competing anions such as Cl−, NO3−, and NO2−. Competing anion exchange experiments and magic-angle spinning (MAS)-NMR spectroscopy of anion-exchanged NDTB-1 demonstrate that this unprecedented selectivity originates from the ability of NDTB-1 to trap TcO4− within cavities, whereas others remain mobile within channels in the material. The exchange kinetics of TcO4− in NDTB-1 are second-order with the rate constant k2 of 0.059 s−1 M−1. The anion exchange capacity of NDTB-1 for TcO4− is 162.2 mg g−1 (0.5421 mol mol−1) with a maximum distribution coefficient Kd of 1.0534 × 104 mL g−1. Finally, it is demonstrated that the exchange for TcO4− in NDTB-1 is reversible. TcO4− trapped in NDTB-1 can be exchanged out using higher-charged anions with a similar size such as PO43− and SeO42−, and therefore the material can be easily recycled and reused.