A series of copper and 1,3-phenylebis(azanetriyl)tetrabenzoate based MOFs were obtained by postsynthetic modification of DUT-71 (DUT = Dresden University of Technology) using various nitrogen containing, neutral ligands to afford the compounds DUT-74, DUT-95, DUT-112, and DUT-114. The structure of the new MOFs DUT-112 and DUT-114 was solved from synchrotron X-ray single-crystal diffraction data. Both structures are tetragonal (P4/mnc) but differ slightly in the lattice parameters. All materials show specific shifts in absorption bands in solid state UV/vis spectra as a response to the exposure to various analytes. Analyzing this shift, it was possible to distinguish between solvents differing in polarity. Moreover, the determination of the polar analyte content in the excess of lower polarity solvent at low concentrations of 0.01 wt % is feasible.