Design and construction of cobalt-organic framework with outstanding adsorption properties assembled by 3-(3,5-dicarboxylphenoxy)pyridine

•Two novel Co-mofs show unparalleled topologies frameworks.•Co-MOF 2 has proposed ultra-high adsorption capacity on CR (capacity: 810.7 mg g-1).•Co-MOF 2 has excellent adsorption potential in CR from the real wastewater. Removal the hazards of Azo organic dyes from waterbody through porous heterogeneous materials is considered as a low-cost and high-efficient method. Intriguingly, two metal organic frameworks (MOFs), {[Co3(L)3(H2O)]·3.5(C4H2O2)}n and [Co4(L)4(bit)2]n designated as MOF 1 and 2, have been synthesized through the traditional solvothermal method. MOF 2 exhibits significant removal effect on organic dye (congo red (CR)) from waterbody owing to more imidazole rings in the structure than 1. After optimizing the experimental conditions, the highest adsorption capacity (810.7 mg g-1) and high removal rate (97.28%) of 2 are obtained in 500 ppm CR solution. Pseudo second-order kinetics and Langmuir isotherms more accurately described the adsorption process of 2. In addition, 2 exhibits high recyclability, stability and adsorption performance through a simple organic solvent release system. Moreover, 2 also exhibits high adsorption performance in real wastewater. The possible mechanism of selective adsorption involves the π-π stacking interaction, hydrogen bond, synergistic effect of electrostatic interaction and pore filling. All the bench experiments have indicated that 2 is a promising potential sorbent in the practical wastewater treatment and CR dyes recovery. Preliminary screening displays that 2 has proposed ultra-high adsorption capacity on CR, and its maximum adsorption capacity could reach 810.7 mg g-1. In addition, the adsorption process in accordance with the Langmuir isothermal model and the second-order kinetic model. Even in dye mixtures, CR could be selectively adsorbed, and the removal rate maintained 88% after six cycles. Finally, through dye classification, infrared analysis, SEM and BET tests, it was supposed that the adsorption of CR by 2 with the synergistic of electrostatic, π-π stacking and hydrogen bond interaction. In actual river water, the maximum adsorption capacity is as high as in bench results in deionization system. Therefore, our work provided 2 has excellent adsorption performance and potential application in CR extraction from the real wastewater. [Display omitted]