Metal-organic frameworks (MOFs), particularly ELM-11, are promising sorbents for CO2 capture due to their gate-opening phenomenon and excellent reusability. Since actual exhaust gases contain impurities such as NO2, in this study, the effect of NO2 on the CO2 sorption performance of ELM-11 was investigated. ELM-11 was exposed to 1000 ppm NO2 for varying durations, ranging from short to long, and subsequent CO2 sorption was evaluated using several methods: gravimetric analysis (TG-DTA), volumetric analysis (sorption isotherms), FT-IR spectroscopy (to detect chemical bond changes), TG-MS (to analyze decomposition products), and PXRD (to observe structural changes). The TG-DTA results indicated that long-term NO2 exposure (e.g., 20 h) generally reduced CO2 sorption, whereas short-term exposure (3 h) could enhance it. This finding was supported by volumetric sorption isotherm measurements. FT-IR and TG-MS analyses revealed that NO2 underwent both physical and chemical sorption in small amounts, with chemical sorption occurring through reactions with Cu2+ ions. Consequently, 20 h of NO2 exposure resulted in approximately a 6 or 10% reduction in CO2 recovery capacity. However, since the degradation was only 6 or 10% despite exposure to a relatively high concentration of NO2 (1000 ppm), these results suggest that ELM-11 exhibits high resistance to NO2, making it suitable for practical applications.
Luo et al. (2026) studied this question.