A new
family of organic–inorganic hybrid layered materials
based on cadmium and zinc sulfates was synthesized using 1,2-phenylenediamine
(OPD), 1,3-phenylenediamine (MPD), and 1,4-phenylenediamine
(PPD) as organic templates and ligands. The diamines
act as structure-directing agents to obtain one-dimensional (1D),
2D, and 3D frameworks. Six new materials were obtained utilizing a
simple, solvent-free synthesis approach: 1D: (OPD)2ZnSO4
1, (OPD)2CdSO4
2; 2D: (MPD)2ZnSO4
3, (MPD)2CdSO4
4; 3D: (PPD)ZnSO4
5, (PPD)CdSO4
6. The
synthesis method proved to be scalable and robust. The crystal structures
were determined using data from X-ray powder diffraction measurements
(XRPD). It was observed that the type of amine determines the dimensionality
of the obtained materials. 1D, 2D, and 3D structures were obtained
using ortho-, meta-, and para-phenylenediamine isomers, respectively. The phase purity
of the samples was confirmed by elemental analysis, and the morphology
of the crystallites was studied using scanning electron microscopy.
The thermal stability was determined by thermogravimetry and nonambient
XRPD techniques. Additional characterization was performed for the
two non-centrosymmetric, polar materials 3 and 4. Second-order nonlinear optical properties were examined
using both experimental measurements (second harmonic generation)
and theoretical calculations.