Structural Diversity of Lanthanum–Organic Frameworks Based on 1,4-Phenylenebis(methylene)diphosphonic Acid

The preparation of five different compounds, [La 2 (H 2 pmd) 3 (H 2 O) 12 ] ( 1: 1D), [La 2 (H 2 pmd)(pmd)(H 2 O) 2 ] ( 2: 3D), [La(H 3 pmd)(H 2 pmd)(H 2 O)] ( 3: 3D), [La 2 (H 2 pmd) 3 (H 2 O) 2 ] ( 4: 3D), and [La 2 (H 2 pmd)(pmd)(H 2 O) 4 ] ( 5: 3D), as crystalline materials from the reaction of 1,4-phenylenebis(methylene)diphosphonic acid (H 4 pmd) with lanthanum chloride is reported. Two different, fast, and economically viable synthetic approaches were employed with their various parameters being probed and, when possible, optimized to increase yields and purity: microwave-assisted synthesis (MWAS, in ca. 1 min) and a bench procedure using standard ambient conditions (one-pot, ca. 10 min). Compounds 1 and 2 were isolated as phase-pure crystalline materials. Compounds 3 and 4 were characterized by single-crystal X-ray diffraction from mixtures, and compound 5 was identified by powder X-ray diffraction studies (also from a physical mixture with 2 ). Structural details for all compounds were investigated by using in tandem X-ray diffraction (single-crystal and powder), electron microscopy (SEM and EDS), and FT-IR spectroscopy. Topological studies were also performed for all 3D networks. The conversion of compound 1 (1D) into 3D networks was investigated using hydrothermal, microwave, and one-pot methods: 1 was totally converted into phase-pure 2 via the hydrothermal method and one-pot method.