Exploring the dicationic gemini surfactant for the generation of mesopores: a step towards the construction of a hierarchical metal–organic framework†
The present study demonstrates a soft-template-assisted synthesis route to the preparation of a hierarchical microporous–mesoporous Cu-BTC metal–organic framework. The supramolecular assembly of di-cationic quaternary ammonium structure-directing agents cooperatively interacts with Cu-BTC framework coordination layers via a weak electrostatic interaction and self-assemble to form a Cu-BTC framework containing a hierarchical system of mesopores interconnected with micropores. Pore-size distribution measurements revealed that the produced metal–organic framework has a bimodal pore-size distribution consisting of micropores and mesopores. Materials prepared with the di-cationic structure-directing agent and swelling agent 1,3,5-trimethyl benzene showed further improvement in the mesopore diameter. The hierarchical Cu-BTC framework demonstrated higher CO2 uptake capacity and better oxidation activity in reactions involving large molecules, when compared to the conventional Cu-BTC framework.