Fabrication of granular MOF@γ-Al2O3 composites as promising dual-function adsorbents for the efficient capture of iodine and dyes

As reported herein, we have designed an effective way to achieve in-situ loading of metal-organic frameworks (MOFs) into the pores of activated γ-Al2O3 particles to prepare low-cost, easy-to-obtain and high-yield granular MOFs composites (GMCs). MOF-5, ZIF-8, Ni-BTC, and Co-BTC have been selected to prepare GMCs via in-situ synthesis methods, thereby leading to the GMCs MOF-5-X@γ-Al2O3, ZIF-8-X@γ-Al2O3, Ni-BTC-X@γ-Al2O3, and Co-BTC-X@γ-Al2O3 (X = NO3 or OAc), respectively. The physical and chemical properties of the as-prepared MOF@γ-Al2O3 GMCs were characterized in detail. The results show that MOF-5-X@γ-Al2O3 and ZIF-8-X@γ-Al2O3 exhibit selective adsorption behavior for anionic dye. The adsorption capacities of MOF-5-X@γ-Al2O3 are 1388.01 mg g−1 (for CR and X = NO3), 1431.25 mg g−1 (for CR and X = OAc), 406.50 mg g−1 (for MO and X = NO3), and 234.16 mg g−1 (for MO and X = OAc), respectively, while the adsorption capacities of ZIF-8-X@γ-Al2O3 are 1426.85 mg g−1 (for CR and X = NO3), 1543.91 mg g−1 (for CR and X = OAc), 477.03 mg g−1 (for MO and X = NO3), and 451.02 mg g−1 (for MO and X = OAc), respectively. Moreover, ZIF-8-X@γ-Al2O3 has high adsorption performance for iodine molecules in solution, and the adsorption capacity reaches 630.63 mg g−1 for ZIF-8-NO3@γ-Al2O3 and 583.92 mg g−1 for ZIF-8-OAc@γ-Al2O3, respectively. This method is universal and can be used as an effective approach to prepare GMCs. In addition, the materials prepared by this method can be widely used in the adsorption of small molecules.