Pb(II) Coordination Polymers: Crystal Engineering, Photophysical Behavior, and Mechanistic Insights Into Acetone Detection

Two new Pb(II)‐based coordination polymers (CPs) with chemical formulas, [Pb(L 1 ) 2 (H 2 O)] n (CP 1 ) and [Pb(L 2 )(DMF)] n (CP 2 ), were synthesized under solvothermal conditions using adamantane‐1‐carboxylic acid (HL 1 ) and 5‐nitroisophthalic acid (H 2 L 2 ) as organic linkers. Single‐crystal X‐ray diffraction shows that CP 1 adopts a 1D chain structure built from mixed chelating/bridging μ 4 ‐adamantane carboxylates and aqua ligands, while CP 2 forms a robust 2D sheet network supported by μ 3 / μ 4 carboxylate modes of H 2 L 2 {L 2 2‐ } and coordinated DMF. Photophysical studies reveal ligand‐centered enhanced fluorescence upon coordination to Pb(II), attributed to framework‐induced rigidity of the HL 1 and π ‐conjugated H 2 L 2 linkers. Both CPs show negligible response toward metal ions, anions, and amino acids. However, they display highly selective fluorescence quenching toward acetone. Both CP 1 and CP 2 exhibit low detection limits (LOD) of 24.22 μM and 3.32 μM, respectively. Stern–Volmer analysis, complemented by density functional theory calculations, indicates that acetone‐induced quenching is attributed to a photoinduced electron transfer (PET) pathway, facilitated by the energy‐level alignment and weak host–guest interactions including possible hydrogen bonding between acetone and the framework of CPs 1 and 2 . Notably, both CP 1 and CP 2 are recyclable over five cycles with minimal loss in the sensing activity.