Smart NIR-Emitting Organometallo Pt(II)-Ionosilica Aerogel for Selective Au(III) Sensing and Recovery

We present a novel one-pot synthesis of a luminescent hybrid aerogel that employs an alkoxysilane-functionalized cyclometallated platinum(II) complex as both cross-linking agent and photoactive unit. This ionic material consists entirely of cyclometallated platinum(II) cations and their corresponding PF₆ ^- counterions. This method eliminates the need for external silica precursors, enabling the scalable fabrication of robust 3D silica networks with homogeneously integrated functional moieties. The aerogel features a bimodal meso-/macroporous framework with a surface area (∼300 m²/g) two orders of magnitude higher than its xerogel counterpart. The material exhibits NIR phosphorescence originating from ³MMLCT transitions. Due to the synergy between its high porosity and photoluminescence, the aerogel exhibits excellent sensing capabilities toward [AuCl₄]^-, as evidenced by emission quenching. Experimental and theoretical studies point to an unprecedented Pt(II)···Au(III) metallophilic interaction, shedding light on the gold adsorption mechanism. Remarkably, the material fully restores its luminescent properties upon removal of gold species, enabling multiple sensing and recovery cycles, thus enhancing practical applicability. This study introduces a multifunctional hybrid platform that integrates optical functionality, structural robustness, and metal selectivity, expanding the application of smart aerogels in sustainable sensing and resource recovery.