Through the use of high-throughput methods, solvothermal reactions of FeCl3 and 2-aminoterephthalic acid in protic as well as aprotic reaction media were systematically studied. Thus, the fields of formation of the isoreticular structures of MIL-53, MIL-88, and MIL-101 based on Fe(III) and aminoterephthalate could be identified for the first time. The resulting 3D framework materials with amino-functionalized pores have been characterized using X-ray diffraction; IR spectroscopy; and thermogravimetric, elemental, and energy dispersive X-ray analysis. Due to the applied high-throughput method, a high density of information was obtained in a short period of time, which allows the extraction of important reaction trends and contributes to a better understanding of the role of compositional as well as process parameters in the synthesis of inorganic-organic hybrid materials. We have found that the nature of the reaction medium has the most profound impact on structure formation. Furthermore, the concentration of the starting mixture (i.e., the solvent content) and the temperature have also been identified as key parameters for the formation of the different hybrid phases.