A novel granular MOF composite with dense and ordered MIL-100(Fe) nanoparticles grown on porous alumina: Green synthesis and enhanced adsorption of tetracycline hydrochloride

Powdery MOF adsorbents have great application potential in the field of water treatment, though the engineering of powdery MOF used in practical applications has so far been a major barrier. Here, a green and facile technology without the addition of surfactant or binder was developed to prepare the MOF composites in granular form. Characterizations suggest that MOF nanocrystals were densely and orderly distributed on the commercially available activated Al 2 O 3. The pre-mixing of metal precursor of MOF with activated Al 2 O 3 was shown to be essential, which provided abundant nucleation sites for the self-assembly growth of MOF crystals on the activated Al 2 O 3 support. The granular composites with low MOF loading ( ca. 3 wt%) displayed better adsorption efficiency (95%) for tetracycline hydrochloride within 60 min compared with the activated Al 2 O 3 (51%) and MIL-100(Fe) (where MIL — Materials of Institute Lavoisier) powder alone (72%). Results show that the composites had wide pH applicability (4 ~ 10) and were insignificantly influenced by the presence of certain inorganic ions, except for carbonate, and fulvic acid in solution. Moreover, the composites possessed easy operability, excellent recyclability and good regenerability by photolysis. It was the synergistic interactions between the MIL-100(Fe) layer and activated Al 2 O 3 support that led to the superior adsorptive performance of granular MOF composites. MIL-68(Al) loaded on activated Al 2 O 3 was also successfully realized, evidencing the effectiveness of the newly developed synthesis route. This work presented an economical and valuable way for the preparation of MOF composites in granular form with unique properties, which are very promising for the industrial application.