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.