Cd-Based Coordination Frameworks with Multiple Optical Properties: Tunable RTP, Photochromism, and SHG Efficiency

In this study, we utilized the pyridine derivative tri(pyridin-3-yl)amine (TPA) and terephthalic acid (H₂PTA) as coordination ligands to synthesize two Cd-organic frameworks, namely [Cd₃(PTA)₃(TPA)] (1) and [Cd₃(PTA)₃(TPA)(DMA)]•2DMA (2) (DMA = N,N-dimethylacetamide). It was demonstrated that both compounds possess room-temperature phosphorescence (RTP). Specifically, compound 1 exhibited an interesting excitation-responsive RTP emission, with the phosphorescence covering half of the visible spectrum, while compound 2 was found to display a distinct blue-green phosphorescence. The photochromic behaviors of solids 1 and 2 were monitored, and the combination of this fascinating property with fluorescence and phosphorescence provides a simple approach for triple-message security encryption. In addition, due to its noncentrosymmetric structural nature, compound 2 showed a second harmonic generation effect, which is comparable to that of KH₂PO₄ at 1064 nm.