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Two-dimensional (2D) halogen-bonded organic frameworks were readily engineered by strong and directional effects of the primary Br⋯O and the secondary Br⋯π halogen bonding interactions from the tetrabromobenzene-1,4-dicarboxylic acid (H2Br4BDC) building molecule involving 100% supramolecular yields. The 2D assembly can function as a host layered framework for the intercalation of various guest solvents including acetone (ATN), ethanol (EtOH), dimethyl sulfoxide (DMSO), and ethylene glycol (EG) resulting in a 1 : 2 host : guest complexation stoichiometry viz. H2Br4BDC·2S (S = ATN (1ATN), EtOH (2EtOH), DMSO (3DMSO), and EG (4EG)). All the solvates show remarkable similarities in their 2D layered sheets and the bilayer distance significantly responds to the size, shape, molecular conformation, and strength of the hydrogen bonding capability of the intercalated solvent molecules. The transition between solvate formation and desolvation was found to be facile and reversible upon the desolvation-resolvation process. The estimated Br⋯O halogen bonding energy of the solvates is in the -0.6 to -1.7 kcal mol-1 range, which was determined by quantum-mechanical calculations based on density functional theory (DFT) calculations. Furthermore, to quantitatively identify the host-guest intermolecular interactions of these solvates, they were visually compared by Hirshfeld surface analysis.

Fourteen three-dimensional (3D) lanthanide coordination polymers (CPs) with dicarboxylate mixed ligands, [Ln(fum)(1.5)(H2O)(2)]center dot 0.5(H(2)bdc)center dot H2O (Ln = Sm (1), Tb (2)), [Ln(2)(fum)(2)(bdc)(H2O)(4)]center dot 2H(2)O (Ln = Sm (3), Eu (4), Tb (5), Er (6)), [Ln(fum)(0.5)(bdc)] (Ln = Sm (7), Eu (8), Tb (9), Er (10)), and [Ln(2)(bdc)(2)(ox)(H2O)(4)]center dot 0.7H(2)O (Ln = Sm (11), Gd (12), Tb (13), Dy (14)), have been synthesized hydrothermally from the self-assembly of lanthanide(iii) ions (Ln(3+)), fumaric acid (H(2)fum), and terephthalic acid (H(2)bdc) in the presence of potassium hydroxide at different temperatures. The compounds fall into four classes. Compounds 1 and 2 were isolated from hydrothermal reactions performed at a relatively low temperature of 100 degrees C and found to crystallize in the triclinic space group P (1) over bar. The 3D framework is assembled from 2D layers of [Ln(fum)(H2O)(2)] units pillared by the chelating fum ligands and has 1D rhombic channels templated by H(2)bdc and lattice H2O molecules. The framework presents a binodal (4,5)-connected tcs topology with the point symbol (4(4).6(2))(4(4).6(6)). Raising the reaction temperature to 140 degrees C resulted in the formation of compounds 3-6. These materials crystallize in the monoclinic system with the polar space group P2(1) and feature a 3D network constructed from dinuclear {Ln(2)(OCO)(6)(H2O)(4)} units interlinked by fum and bdc ligands, showing a uninodal 6-connected two-fold interpenetrated pcu topology. The small channels of the framework are occupied by lattice H2O molecules. Further increase of the reaction temperature to 160 degrees C gave rise to the formation of compounds 7-10, crystallizing in the orthorhombic space group Pbca. The 3D framework is generated from 2D corrugated sheets of [Ln(fum)](2+) bound by bdc ligands and contains no intercalated H2O molecules in the lattice. The framework possesses a trinodal (4,6,7)-connected net with the point symbol (