Cu(II)-Based Coordination\nPolymers Containing 1,4-Bis(1<i>H</i>‑imidazol-1-yl)benzene\nand Monovalent Fluorinated\nAnions

The design of the organic linker is one of the most important\nsteps\nin driving the formation of the desired crystal structure in coordination\npolymers. Imidazole derivatives exhibit wide and interesting coordination\ncapabilities. This property makes these π-conjugated ligands\nsuitable linkers in the synthesis of metal–organic frameworks\n(MOFs). Despite these considerations, few examples of two-dimensional\n(2D) materials based on the 1,4-bis(1<i>H</i>-imidazol-1-yl)benzene\n(<b>bib</b>) ligand, which can be seen as a topological analogue\nof 4,4′-bipyridine, have been reported so far, and there is\na lack of literature on the exploration of their gas adsorption properties.\nThe combination of <b>bib</b> ligand with Cu(BF<sub>4</sub>)<sub>2</sub> led us to obtain a doubly interpenetrated three-dimensional\n(3D) material (<b>UdP-1</b>) of minimal formula [Cu(<b>bib</b>)<sub>2.5</sub>(BF<sub>4</sub>)]·(BF<sub>4</sub>)·1.5H<sub>2</sub>O that loses 0.5 equiv of <b>bib</b> upon heating and\nundergoes a phase transition to a new material named <b>UdP-2</b>. <b>UdP-2</b> was obtained as a microcrystalline powder by\ndirect synthesis, but its crystal structure could not be elucidated.\nAttempts to obtain single crystals of <b>UdP-2</b> led us to\ndiscover four new compounds, named <b>UdP-3</b>, <b>UdP-3-i</b>, <b>UdP-4</b>, and <b>UdP-5</b>, displaying both 2D\nand 3D structures. Using Cu(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> instead of Cu(BF<sub>4</sub>)<sub>2</sub> allowed us to prepare\na 2D layered material of the formula [Cu(<b>bib</b>)<sub>2</sub>(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>]·2MeOH (<b>UdP-6</b>), where the methanol molecules are trapped in the pores of the structure\nas in the ELM-12 structure, which contains 4,4′-bipyridine\nas the organic ligand. Different from ELM-12, <b>UdP-6</b> displays\na Type I CO<sub>2</sub> adsorption isotherm, with no evidence of a\ngating phenomenon. This behavior is attributed to the larger number\nof supramolecular interactions existing between adjacent layers in <b>UdP-6</b>.