Ligand Substitution in Three Organic–Inorganic Hybrid Zincophosphite Analogs: Modulating Lanthanide Affinity and White-Light Emission via Hard–Soft Acid–Base Interplay

Abstract Systematically modulating the structural environment of solid-state materials is critical for tailoring physical–chemical interactions. Here, we demonstrated the synthesis and characteristics of three hybrid zincophosphite frameworks (NTOU-12a, -12b, and -12c) that were designed by using Hard–Soft (HSAB) principles to modulate lanthanide adsorption and luminescence. In the replacement of oxygen-donor dicarboxylate ligands with a sulfur-containing linker (2,5-thiophenedicarboxylic acid), the local coordination environment and structural chemistry were systematically modified while preserving the overall framework architecture. This substitution led to 27–42% and 32–41% decreases in uptake of Eu3+ and Tb3+ ions, respectively. By tuning the ratio of adsorbed Eu3+/Tb3+ on the title compounds, the emission color could be continuously tuned over a wide spectral range. Notably, NTOU-12a exhibited white-light emission under 254 nm excitation. These results demonstrate that rational ligand substitution provides an effective strategy for designing crystalline materials with selective lanthanide adsorption and tunable multicolor luminescence.