Scalable and Cost-Effective Approach for Multiple NO₂ Removal using the MOF-801 Framework

The removal of nitrogen dioxide (NO₂) is becoming increasingly critical due to its rising concentration in the atmosphere, driven by growing exhaust emissions and industrial production. However, many types of sorbents degrade due to the high reactivity of NO₂, rendering them unsuitable for cyclic use. In this study, a low-cost and scalable approach is proposed to apply and regenerate zirconium-based MOF-801 framework for NO₂ removal from gas mixtures, allowing its reuse multiple times. Through in situ electron paramagnetic resonance (EPR) spectroscopy, ex situ ATR-FTIR spectroscopy and breakthrough measurements, the mechanism of NO₂ sorption in MOF-801 is elucidated. The majority of the sorption capacity is attributed to the formation of nitrates and nitrites, which can be conveniently eliminated from the sorbent. To facilitate this process, a novel regeneration method using low-cost chemicals is developed. The effectiveness of MOF-801 exposed to low concentrations of NO₂ (400 ppm, typical for the flue gases) is demonstrated in breakthrough experiments. The whole cycle of NO₂ adsorption, product removal, and sorbent regeneration can be employed repeatedly for capturing NO₂ from dilute mixtures, paving the way for practical environmental applications.