Study on the Synthesis of 2D[Ni(tib)(mpda)(H2O)2]·H2O and Its Adsorption to Remove Methyl Orange in Water
Porous coordination polymers have attracted significant attention due to their tunable structure,large specific surface area,excellent selectivity,stability and reproducibility,making them ideal adsorbents for removing dyes from wastewater.In this paper,a coordination polymer called[Ni(tib)(mpda)(H2O)2]·H2O was synthesized using flexible m-phenyldiacetic acid(mpda)and rigid 1,3,5-tris(1-imidazolyl)benzene(tib).In[Ni(tib)(mpda)(H2O)2]·H2O,the tib acts as a trinode coordinating to the Ni(Ⅱ)ion,forming a 2D lattice surface.The cis-mpda is attached to the 2D lattice surface in a telomeric fashion.The uncoordinated carboxylate group O of the mpda forms a 3D supramolecular network structure through O—H … O interactions with a coordinating water molecule(O0… O3 0.2624 nm,∠O5-H5A …O2=155.41°).The thermal stability,phase purity,and specific surface area of[Ni(tib)(mpda)(H2O)2]·H2O were also examined in the study.It was found that the polymer's skeleton begins to decompose and collapse at 316℃.The highly pure crystalline material had a specific surface area of 58 m2/g and average pore size of 15.47 nm.The[Ni(tib)(mpda)(H2O)2]·H2O was shown to effectively remove methyl orange dye in an aqueous system,with an adsorption capacity of 18.64 mg/g.The adsorption data are fitted well with the Langmuir model and the proposed second-order kinetic equation,indicating that the adsorption process is a monolayer chemisorption.The adsorption of anionic dye-methyl orange is the largest at pH=4,and the ζ potential of[Ni(tib)(mpda)(H2O)2]·H2O indicates that the surface has positive charges,validating the adsorption force mainly from electrostatic interaction.Moreover,thermodynamic studies reveal that the adsorption process is spontaneous and exothermic,and results in entropy reduction.
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