Spray synthesis of hierarchical porous metal-organic framework HKUST-1 with soft templates and methylene blue adsorption performance

We synthesize hierarchical porous HKUST-1 (HP-HKUST-1) with micropores, mesopores, and macropores using the spray synthesis and soft template methods. We utilize two types of structure-directing agents (SDAs), namely cetyltrimethylammonium bromide and citric acid for C-HKUST-1 and triblock copolymer P123 for P-HKUST-1. Paq-HKUST-1 is successfully synthesized using only water as the solvent. The volumes of the mesopores and macropores are changed by the amounts of SDAs. The highest values are: 0.78 and 0.30 cm3/g for C-HKUST-1; 0.44 and 0.38 cm3/g for P-HKUST-1; and 0.30 and 0.23 cm3/g for PaqHKUST-1, respectively. HP-HKUST-1 shows high methylene blue (MB) adsorption rates and capacities of over 700 mg/g owing to its HP structure. In particular, C-HKUST-1 exhibits a rate constant of 19.7 mg/mg min for MB adsorption based on the pseudo-second-order adsorption kinetic model. This rate constant is 10 times higher than that of batch-synthesized HKUST-1. Furthermore, HP-HKUST-1 exhibits good stability for reuse as an MB adsorbent. (c) 2023 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.