Fabrication of a Cd(ii) metal–organic framework as a dual functional material: efficient iodine capture and selective adsorption of a cationic dye

Abstract

Effectively capturing radioiodine that is created or released as a result of nuclear fission is crucial for environmental protection. Metal–organic frameworks (MOFs) may be useful materials in this case to aid with the problematic environmental issue. The solvothermal reaction of Cd(II) salt with rigid terephthalic acid (H₂tpa) and 1,2,4-triazole (Htz) builds a novel MOF, [Cd₂(tpa)(tz)₂(DMF)₂] (FV-1). According to single crystal XRD, FV-1 has a 3D framework with a 3,4-connected rare dmc topological network with the Schläfli point symbol {4·8²}{4·8⁵}. The as-prepared MOF was meticulously characterized, and its iodine adsorption in the vapour and solution phases was also examined by UV-vis spectroscopy, with the adsorption capacity being extremely high. FV-1 has a maximum sorption capacity of around 0.554 and 0.301 g g⁻¹ in the vapour and solution phases, respectively, with a recyclability of up to four cycles. Iodine binds to the MOF in the forms of I₂ and I₃⁻ species, according to XPS and Raman spectra. Interestingly, DFT studies on iodine sorption to study the mechanism of binding with FV-1 prove that along with other interactions, the O⋯I interaction predominates to result in high uptake of iodine. Moreover, a cationic dye, methylene blue (MB), can be very effectively and selectively adsorbed and separated (at pH = 7 and room temperature) by FV-1, and the MOF retains the same adsorption capacity even after repeated cycles. Thus, the present MOF acts as a dual functional material for higher iodine uptake and efficient cationic dye adsorption.