Two zinc phosphate layered materials, each containing unique 3-rings yet differing hydrogen bonding schemes, have been prepared by hydrothermal methods and characterized by single-crystal X-ray diffraction, TGA, and MAS NMR. These phases consist of a two-dimensional network of (\mathrm{ZnO}{4}) and (\mathrm{PO}{4}) tetrahedra, linked through oxygen vertices, to form structures whose interlayers are occupied by charge-balancing cations. The layers are notable because of the formation of 3-rings comprised of the tetrahedral atoms, (\mathrm{Zn}) and (\mathrm{P}), and the oxygen atoms, resulting in "terminal" - (\mathrm{OH}) bonds off the (\mathrm{P}(2)) atom, in the sodium analog, and off the (\mathrm{P}(\mathrm{I})) atom in the cesium analog. The topology of the layers is controlled by the templating cation. While the small interlayer sodium cation allows for hydrogen bonding between the layers which results in "puckered" sheets, the larger cesium cation does not allow interlayer hydrogen bonding, resulting in flat sheets. Sodium hydrogen zinc orthophosphate (\left(\mathrm{NaH}\left(\mathrm{ZnPO}{4}\right){2}\right)) is a triclinic crystal: space group P1 (no. 2), with (a=8.641) (2), (b=8.817) (3), and (c) (=5.1268) (9) (\AA βΏ» \alpha=100.401(8)^{\circ}, \beta=105.684(8)^{\circ}), and (\gamma=96.924(9)^{\circ} ; V=363.9(1) \AA^{3}) and (Z=2), with (R=5.21 %) and (R_{w^{\prime}}=4.96 %) for 1873 observed reflections, according to the criterion (I>3 \sigma(I)), Cesium hydrogen zinc orthophosphate (\left(\mathrm{CsH}\left(\mathrm{ZnPO}{4}\right){2}\right)) is orthorhombic: space group (A b m a) (no. 64), with (a=7.739(8), b=6.594) (7), and (c=15.94) (2) (\AA ; \alpha=90^{\circ}, \beta=90^{\circ}), and (\gamma=90^{\circ} ; V=813.56) (5) (\AA^{3}) and (Z=4), with (R=4.56 %) and (R_{w^{\prime}}=5.23 %) for 762 observed reflections, according to the criterion (I>3 \sigma(I)). 1993 Academic Press, Inc.