A Pnictogen-Rich Microporous Zn(II) Metal–Organic Framework as a Multifunctional Platform for Gas Separation, Luminescent Sensing, and Photocatalytic Applications

The rational design of multifunctional metal–organic frameworks (MOFs) that integrate sensing, photocatalysis, and selective gas separation remains a key objective in coordination chemistry. A cyclotriphosphazene-derived 3D Zn(II) MOF ( PCP-19 ), {[Me 2 NH 2 ] 2 [Zn 2 (L)( bmimb )]·solvent} n, featuring a nitrogen- and phosphorus-rich microporous architecture, has been synthesized and structurally characterized as a multifunctional platform for luminescent sensing, photocatalysis, and selective gas adsorption. The framework exhibits robust structural stability together with Zn(II) centers in distorted tetrahedral coordination environments and electron-rich cyclophosphazene units, enabling cooperative host–guest interactions within confined micropores. Although Zn(II) sites may contribute weakly as Lewis acidic centers, the adsorption behavior is primarily governed by micropore confinement and the electron-rich pore environment. PCP-19 displays sensitive fluorescence responses toward Fe 3+ ions and nitroaromatic compounds together with efficient photocatalytic degradation of methylene blue (MB), achieving up to 94% removal efficiency. Gas adsorption measurements reveal moderate CO 2 uptake (27.04 cm 3 g –1 at 273 K) and notable H 2 adsorption at 77 K, accompanied by moderate isosteric heats of adsorption indicative of physisorption. Remarkably, PCP-19 exhibits very low N 2 affinity at ambient temperature, showing negligible uptake and consequently very high apparent CO 2 /N 2 selectivity, arising from the synergistic effects of micropore confinement and the nitrogen-rich framework. Multifunctional behavior arises from the synergy between pore chemistry, analyte recognition, and adsorption selectivity. These results highlight a clear structure–function relationship in which topology-driven stability and cooperative Lewis acid–base interactions govern molecular recognition, establishing cyclophosphazene-based MOFs as promising candidates for integrated sensing, catalytic remediation, and selective gas separation applications.