Three open-framework iron phosphites: Fe п 5 (NH 4) 2 (HPO 3) 6 (1), Fe п 2 Fe ш (NH 4)(HPO 3) 4 (2) and Fe ш 2 (HPO 3) 3 (3) have been synthesized under ionothermal conditions. How the different synthesis parameters, such as the gel concentrations, synthetic times, reaction temperatures and solvents affect the products have been monitored by using high-throughput approaches. Within each type of experiment, relevant products have been investigated. The optimal reaction conditions are obtained from a series of experiments by high-throughput approaches. All the structures are determined by single-crystal X-ray diffraction analysis and further characterized by PXRD, TGA and FTIR analyses. Magnetic study reveals that those three compounds show interesting magnetic behavior at low temperature.