Encouraged by the excellent accuracy of the ML model on retrospective experimental structures, six new ligands were selected for synthesis, including five predicted stable ligands, F4Tm, 4Te, PPP, PPT, and TP, and one predicted unstable ligand, 4Tm-1C (Figure ,S5). The 4T ligands share a quater-thiophene body and are distinguished by side-chains and linker. The F4Tm has a fluoride substituent at the αposition of the outer thiophene while 4Tm-1C has only one methylene as the linker, which leads to its predicted instability. Both F4Tm and 4Tm-1C have two methyl side-chains for solubility while 4Te has two ethyl side chains on the outer and one inner thiophenes. Ethyl solubilizing groups have never been reported in a 2D-perovskite phase but were nevertheless predicted to be stable with this body by the ML model. TP, PPT, and PPP represent body chemistries that were outside of the training data. TP contains a large fused-ring system with a 2C-O linker. PPP and PPT both terminate with an ortho-substituted methyl biphenyl unit that is sterically crowded and increases the cross-section of the ligands. Synthetic details can be found in the Methods section. After spin-coating and thermal annealing, thin films of the putative 2D perovskites with these ligands were characterized using thin-film powder X-ray diffraction (Figure ). The films corresponding to F4Tm, 4Te, PPP, PPT, and TP exhibit equal-distance diffraction peaks with corresponding d-spacings of 32.8 Å(2θ=2.69 • ), 34.8 Å(2θ=2.54 • ), 29.2 Å(2θ=3.02 • ), 28.5 Å(2θ=3.10 • ), and 26.3 Å(2θ=3.35 • ), respectively, consistent with the formation of layered 2D Ruddlesden-Popper phase perovskites. Sufficient size and quality crystals could be obtained for F4Tm2PbI4 and PPT2PbI4 to obtain single-crystal structures of the 2D Ruddlesden-Popper phase perovskites (Figure ). For PPT2PbI4 and F4Tm2PbI4, the ∆⟨σ 2 ⟩ calculated from the crystal structures correspond to 15.2 deg 2 and 14.0 deg 2 , respectively. These values are significantly larger than that of crystals of BA2PbI4 (BA=butylammonium), 10.3 deg 2 . Although single-crystal structures could not be solved for 4Te2PbI4, PPP2PbI4, and TP2PbI4, supporting characterizations from GIWAXS and UV-Vis were also consistent with 2D RPphase formation and can rule out the formation of 1D perovskite, PbI2 phases, and other side-products (Figure ). Additional details and results on single-crystal growth are discussed in Supporting Information. We were unable to form a perovskite using the predicted unstable ligand, 4Tm-1C, despite several formulation attempts, changing PbI2 to SnI2, varying annealing temperature, and attempting to grow single crystals (Figure ). This negative experimental result further illustrates that the low stabilization rate of 1C linker hinders the ligand relaxation in perovskite lattice. For the purpose of validating the framework prediction results, the thin-film powder X-ray diffraction, GIWAXS, and UV-Vis results have provided evidence for 2D Ruddlesden-Popper phase perovskites of five predicted-stable ligands.