A facile synthesis of hierarchically porous Cu-BTC for efficient removal of uranium(VI)

Metal-organic frameworks (MOFs) are promising adsorbents for extraction of uranium(VI) due to their high surface area and abundant active site. However, the smaller pore size (< 2 nm) and harsh synthesis conditions (e.g., high temperature and pressure) severely hinder MOFs practical applications in some cases. Herein, we developed a simple and facile method to prepare hierarchically porous Cu-BTC that contained micropores, mesopores and macropores. The as-synthesized hierarchically porous Cu-BTC showed high uptake capacity (406.9 mg g(-1)) and removal efficiency (99.7%) in the capture of uranium(VI) from an aqueous solution. Thermodynamics results indicate the spontaneous nature of uranium(VI) adsorption process onto hierarchically porous Cu-BTC. In addition, Langmuir isotherm and pseudo-second-order models were found to be more suitable in describing the adsorption process of uranium(VI) than those of Freundlich and pseudo-first-order models. These results indicate that hierarchically porous MOFs obtained from rapid room-temperature synthesis are promising adsorbents for the removal of uranium(VI) from aqueous solutions.