H‑Bonding Interactions Induced Two Isostructural Cd(II) Metal–Organic Frameworks Showing Different Selective Detection of Nitroaromatic Explosives

Two luminescent Cd­(II) metal–organic frameworks (MOFs) were prepared from electron-rich π-conjugated fluorescent ligands. They are isostructural with <b>sql</b> nets. Their strong luminescences can be quenched by a series of nitroaromatic explosives. Notably, <b>MOF 1</b> shows highly selective and sensitive detection of 4-nitrophenol (4-NP), while <b>MOF 2</b> exhibits good responses toward picric acid (PA) compared with other nitroaromatic explosives. This different order of quenching efficiency is because there are H-bonding interactions between <b>MOF 1</b> and 4-NP, while <b>MOF 2</b> lacks these H-bonding interactions. <b>MOF 1</b> displays highly selective and sensitive detection of 4-NP with the high quenching constant (6.74× 10⁴ M^–1) and low detection limit (34.48 ppb), which is better than those of known MOFs. <b>MOF 1</b> and <b>MOF 2</b> have highly sensitive and selective detection of 4-NP and PA in the practical application, respectively