| Autor: |
Akiyama, Ikuho, Kato, Takeshi, Kannaka, Shino, Ito, Akitaka, Ohtani, Masataka |
| Zdroj: |
ACS Applied Materials & Interfaces; May 2024, Vol. 16 Issue: 19 p24816-24822, 7p |
| Abstrakt: |
Flexible metal–organic frameworks (MOFs) have attracted much attention as selective gas adsorption and storage. This report describes boron doping in zeolitic imidazolate framework-7 (B-ZIF-7), which exhibits reversible phase transition during CO2adsorption/desorption. We have successfully prepared B-ZIF-7 coordination networks using boron-bridged benzimidazolate (B(bim)4–) as organic ligands. Powder X-ray diffraction (PXRD) measurements and infrared spectroscopy revealed that B-ZIF-7 has a crystal structure similar to that of ZIF-7 while containing boron bridging in the coordination network. Since B-ZIF-7 forms a cationic coordination network, the guest anions are encapsulated within the pore. CO2adsorption/desorption measurements at 300 K showed that B-ZIF-7(NO3), which contains nitrate ions (NO3–) as guest anions in its pores, exhibits a S-shaped CO2adsorption/desorption isotherm, which is characteristic of gate-opening type MOFs. Compared with ZIF-7, B-ZIF-7(NO3) has superior CO2adsorption capacity in the low-pressure and superior CO2storage capacity. The CO2adsorption and desorption behavior of B-ZIF-7(NO3) was analyzed by in situtemperature-controlled PXRD measurements and thermogravimetric analysis under a CO2atmosphere, and a reversible phase transition was observed. We have also successfully prepared B-ZIF-7(Cl) and B-ZIF-7(OTf) (OTf = CF3SO3–) with different guest anions. The CO2adsorption/desorption behaviors of B-ZIF-7(Cl) and B-ZIF-7(OTf) were significantly different from those of B-ZIF-7(NO3) and ZIF-7. B-ZIF-7(Cl) showed gate opening at a higher pressure than ZIF-7, and B-ZIF-7(OTf) did not show S-shaped CO2adsorption isotherm and showed adsorption behavior in micropores. These results indicate that the CO2adsorption behavior of B-ZIF-7 depends on the interaction between the guest anions and CO2molecules or the cationic framework and the bulkiness of the guest anions. Boron doping in a coordination network with boron-bridged imidazolate ligands is a promising strategy to increase the gas adsorption capability of porous materials. |
| Databáze: |
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