The flux synthesis, solid state synthesis, and characterization of a new aluminate, Cs-2(UO2)Al2O5, are reported.Cs-2(UO2)Al2O5 crystallizes in the tetragonal space group I4(1)/amd with lattice parameters a = 7.3254(2) and c = 30.9849(7) and is constructed from edge-sharing chains of U07 pentagonal bipyramids that are connected to [Al2O5](4-) two-dimensional sheets. The cesium cations, which are heavily disordered, occupy small channels in the a and b directions in the framework structure. The optical properties and ion exchange behaviors are reported along with DFT calculations that support the observed results of the ion exchange experiments.