MIL-101-NH2-TFR and MIL-101-NH2-TFR/Cu2+ as novel hybrid materials for efficient adsorption of iodine and reduction of Cr(VI)

Today, due to the earnest jeopardies of environmental contaminants from various sources and their deteriorating effects on the ecosystem, the adsorption and reduction of these highly toxic pollutants with an efficient and cost-effective protocol can be considered a desirable phenomenon. Herein, a chromium-based metal-organic frame-work (MIL-101-NH2) was modified with thiourea and formaldehyde to form a polymeric layer on the surface (MIL-101-NH2-TFR). The resulting nanohybrid, as an adsorbent, was applied for efficient capture of iodine (I2) molecules from cyclohexane solution. MIL-101-NH2-TFR nanohybrid signified a superior adsorption performance for the capture of I2, compared to the pristine MIL-101-NH2, with a theoretical maximum uptake value of 625 mg/g and adsorption efficiency of 96.9 % through thionyl (C--S), amino, and phenyl groups. The pseudo-second-order rate equation and the Langmuir model were best fitted for the I2 adsorption over MIL-101-NH2-TFR adsorbent. Quantum chemical calculations were conducted to reveal the mechanism of I2 adsorption onto the surface of MIL-101-NH2-TFR. Moreover, MIL-101-NH2-TFR was used to anchor Cu2+ to generate a catalytic system (MIL-101-NH2-TFR/Cu2+) for detoxification of Cr(VI) in the presence of formic acid as an eco-friendly reducing reagent in an aqueous medium. MIL-101-NH2-TFR and MIL-101-NH2-TFR/Cu2+ were reused several times for the adsorption/desorption process and the catalytic reduction, respectively.