Porous Coordination Polymers Containing Pyridine-3,5-Bis(5-azabenzimidazole): Exploration of Water Sorption, Selective Dye Adsorption, and Luminescent Properties

Six novel coordination polymers of Cd­(II) and Zn­(II) have been designed and synthesized using pyridine-3,5-bis­(5-azabenzimidazole), <b>L</b>, and various angular dicarboxylates as linkers. The dicaboxylates used are 4,4′-oxobisbenzoate (OBA), isophthalate (IPA) and 1,4-phenylene diacetate (PDA). All the six complexes are found to exhibit general formula of {[M­(<b>L</b>) (dicarboxylate)]·<i>x</i>DMF·<i>y</i>H₂O}_<i>n</i>. The four complexes containing OBA and IPA exhibited two-dimensional layered structures with grid like cavities of dimensionalities 18 × 15 and 17 × 10 Ų, while those with PDA exhibited 3D-network consisting of CdSO₄ topology. The coordination networks are propagated by M₂(RCO₂)₂ SBUs and exhibit guest accessible volume of 23–33%. The XRPD and gas sorption studies confirm their stability and porous nature. Further, these materials exhibited a greater preference for the adsorption of water or alcohol vapors over nitrogen. The alcohol sorption found to depend on the size of the molecules that is they have shown greater ability to adsorb MeOH compared to isopropanol. The dye adsorption studies show that all these neutral network materials can selectively adsorb cationic dye such as crystal violet. Further, all the complexes exhibited solid state luminescence properties at room temperature