From two-dimensional trapezoid-like layer to three-dimensional porous indium-4,4′-biphenyldicarboxylate MOFs

Abstract

Three new indium coordination polymers formulated as In(phen)(BPDA)1.5 (1), In(OH)(H2O)(BPDA) (2), and In(BPDA)2·Me2NH2·H2O (3) (phen = 1,10-phenanthroline, C12N2H8; H2BPDA = 4,4′-biphenyldicarboxylic acid, C14O4H10; Me2NH = dimethylamine, C2H7N), have been synthesized under hydro(solvo)thermal conditions and characterized by infrared (IR), thermal gravimetric analysis (TGA) and luminescence studies. In the two-dimensional (2D) trapezoid-like layer of 1, three BPDA2− anions and one phen group bind to a seven-coordinated In3+ ion with the distorted pentagonal bi-pyramid geometry. In 2, the extended –In–OH–In– chains are connected through BPDA2− to form a 3D framework. Complex 3 possesses a two-fold interpenetrating structure, which consists of two independent infinite diamond-like frameworks with point symbol 66. All three samples exhibit varied solid-state fluorescence: emissions at 468 nm (intense blue), 559 nm (greenish-yellow), and 577–645 nm (broad intense orange band with a maximum at 611 nm, λex = 257 nm) for 1, 567 nm (weak greenish-yellow, λex = 344 nm) for 2, and 480 nm (intense greenish-blue, λex = 385 nm) for 3.