Green synthesis of Sn(II)-BDC MOF: Preferential and efficient adsorption of anionic dyes

Tin metal-organic framework [Sn(II)-BDC MOF] was synthesized following the hydrothermal synthesis route in environmentally benign conditions. The material was applied for preferential and efficient removal of toxic anionic dyes viz. CR, EBT, and EY from aqueous solution. The thermal and aqueous stability of the material was confirmed using PXRD and FTIR analysis. Adsorption kinetic study and the thermodynamic parameters were also investigated. A better fit with the second-order kinetic model indicated that the process is predominantly chemisorption. The Langmuir and Freundlich isotherm models were used for validating the experimental data, where the Langmuir model provided a good fit. The maximum adsorption capacity (qm) for three anionic dyes (CR, EBT, and EY) was 95.2 mg g−1, 125 mg g−1, and 208.3 mg g−1, respectively. The actual evaluation of the adsorption performance was based on the partition coefficient (PC) values. At an initial concentration of 100 mg L−1, the PC values for CR, EBT, and EY were 33.79, 30.29, and 40.44 mg g−1 μM−1, respectively. Based on high PC values and maximum adsorption capacity, Sn(II)-BDC MOF turned out to be an excellent material for the removal of anionic dyes. Further, retention of >86% of its adsorption efficiency after three adsorption-desorption cycles indicated the potential reusability of the synthesized material. This study provides valuable insight into the eco-friendly synthesis of a novel water-stable Sn(II)-BDC MOF and its application as a promising adsorbent in the removal of toxic anionic dyes from aqueous solutions.