Formation of One-, Two-, and Three-Dimensional Open-Framework Zinc Phosphates in the Presence of a Tetramine

Abstract

Five new open-framework zinc phosphates, encompassing the entire hierarchy of open-framework structures, have been synthesized hydrothermally in the presence of triethylenetetramine. The structures include one-dimensional ladders, two-dimensional layers, and three-dimensional structures as well as a zinc phosphate where the amine acts as a ligand. [C6N4H22](0.5)[Zn(HPO4)(2)] (I): monoclinic, space group P2(1)/c (no. 14), a = 5.2677(1) Angstrom, b = 13.3025(1) Angstrom, c = 14.7833(1) Angstrom, beta = 96.049 degrees, Z= 4. [C6N4H22](0.5)[Zn-2(HPO4)(3)] (II)I triclinic, space group P (1) over bar (no. 2), a = 7.515(1) Angstrom, b = 8.2553(1) Angstrom, c = 12.911(1) Angstrom, alpha = 98.654(1)degrees, beta = 101.274(1)degrees, gamma = 115.791(1)degrees, Z = 2. [C6N4H22](0.5)[Zn2P2O8] (III): triclinic, space group P (1) over bar (no. 2), a = 8.064(1) Angstrom, b =8.457(1) Angstrom, c = 9.023(1) Angstrom, alpha = 111.9(1)degrees, beta = 108.0(1)degrees, gamma = 103.6(1)degrees, Z= 2. [C6N4H22](0.5)[Zn-3(PO4)(2)(HPO4)] (IV): triclinic, space group P (1) over bar (no. 2), a = 5.218(1) Angstrom, b = 8.780(1) Angstrom, c = 16.081(1) Angstrom, alpha = 89.3(1)degrees, beta = 83.5(1)degrees, gamma = 74.3(1)degrees, Z = 2. [C6N4H20](0.5)[Zn4P4O16] (V): monoclinic, space group P2(1)/c (no. 14), a = 9.219(1) Angstrom, b = 15.239(1) Angstrom, c = 10.227(1) Angstrom, beta = 105.2(1), Z = 4. The structure of I is composed of ZnO4 and HPO4 tetrahedra, which are edge-shared to form four-membered rings, which, in turn, form a one-dimensional chain (ladder). In II, these ladders are fused into a layer. The structures of III and IV comprise networks of ZnO4 and PO4 tetrahedra forming three-dimensional architectures. In V, the amine molecule coordinates to the Zn and acts as a pillar supporting the zinc phosphate layers, which possess infinite Zn-O-Zn linkages. The 16-membered one-dimensional channel in IV and the ZnO3N pillar, along with infinite Zn-O-Zn linkages in V, are novel features. The structure of the open-framework zinc phosphates is found to depend sensitively on the relative concentrations of the amine and phosphoric acid, with high concentrations of the latter favoring structures with lower dimensions.