Two triphenylamine-based luminescent metal–organic frameworks as a dual-functional sensor for the detection of nitroaromatic compounds and ofloxacin antibiotic

Abstract

Two Zn²⁺-based luminescent metal–organic frameworks containing the same components, {[Zn(TIPA)pim_0.5]2H₂O·NO₃}_n (1) and {[Zn(TIPA)(pim)]3H₂O}_n (2) have been synthesized based on a π-electron rich semi-rigid triangular ligand TIPA (TIPA = tris(4-(1H-imidazol-1-yl)-phenyl)amine and H₂pim = pimelic acid). 1 is a two-fold interpenetrating 3D framework containing four chiral (10,3)-a subnets, and 2 is merely a 2D + 2D → 2D entangled network, although they were synthesized from the same starting materials. A photoluminescence investigation revealed that the emissions of 1 and 2 entirely originate from the intraligands charge transfer transitions (π → π*). Metal–organic framework 1 can be applied as a dual functional chemical sensor for nitroaromatic (NAC) compounds and antibiotics detection with a high sensitivity and quick response. In addition, the effective detection of nitroaromatic compounds and antibiotics was rationalized by the density functional theory (DFT) calculation of the energy bands of the NAC compounds and antibiotics, which revealed that a photoinduced electron transfer mechanism is largely responsible for the sensing of nitroaromatic compounds, and the resonance energy transfer is largely responsible for the exclusive sensing of ofloxacin (OFX).