Two entangled photoluminescent MOFs of naphthalenedisulfonate and bis(benzimidazole) ligands for selective sensing of Fe3+

Highlights: • Two Zn(II)/Cd(II) MOFs of 1,6-naphthalenedisulfonate and 1,4-bis(benzoimidazol-1-yl)butane are described. • 1 shows a 2D.→3D polythreading framework based on 2D (6,3) brick wall. • 2 shows a 4-fold interpenetrating (10,3)-b network. • Both MOFs have the ability of efficient detection of Fe³⁺. -- Abstract: Two entangled MOFs based on rigid 1,6-naphthalenedisulfonate (1,6-NDS) mixed with flexible 1,4-bis(benzoimidazol-1-yl)butane (bbimb) ligands, [Zn(1,6-NDS)(bbimb)_1.5]·2H₂O (1) and [Cd₂(1,6-NDS)₂(bbimb)₃(H₂O)₄]·2H₂O (2), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric and photoluminescent analyses. In 1, the Zn(II) ions are connected by bbimb ligands into a 2D (6,3) brick wall structure with the 1,6-NDS^2- as dangling arms threaded into the voids of two adjacent layers up and down, and finally generates a 2D→3D polythreading framework. While the Cd(II) centers in 2 are connected by bbimb ligands into a 3D (10,3)-b network, and four (10,3)-b networks interweave to generate a 4-fold interpenetrating structure. 1 and 2 dispay similar photoluminescence at 343 nm (λ_ex = 302 nm) and 342 nm (λ_ex = 293 nm), respectively. And both MOFs display selective sensing of Fe³⁺ through the luminescent quenching experiments.