Engineering 2D Mg-Al-layered double oxides with highly dispersed and enhanced basic sites for efficient ambient NO2 reactive removal

The release of nitrogen dioxide (NO2) into the atmosphere significantly contributes to air pollution, posing threats to both the environment and human health. Selective adsorption technologies have gained attention for their potential to mitigate NO2 emissions under ambient conditions. However, certain solid adsorbents lack accessible active basic sites, a crucial requirement for high NO2 adsorption capacities due to the acidic nature of NO2. Metal-based layered double oxides (LDOs), derived from layered double hydroxides (LDHs), show promise for ambient NO2 adsorption due to their layered structures, strong basic properties, and adjustable adsorption affinity. In this study, we synthesized a series of M-Al-LDO/A (M = Ni, Co, and Mg) using a facile aqueous miscible organic solvent treatment (AMOST) method. The newly synthesized M-Al-LDO/A exhibited a 2D nano flower-like morphology with expanded surface area, increased pore volume, and enhanced accessible basic sites. Dynamic breakthrough experiments demonstrated the exceptional NO2 adsorption capacity of Mg-Al-LDO/A (4.67 mmol g-1) under ambient conditions, surpassing Mg-Al-LDO/CP (0.13 mmol g-1) synthesized from the conventional method by more than 35 times. Temperature-programmed desorption (TPD) results and spectroscopic analyses revealed that the improved NO2 capacity of Mg-Al-LDO/A resulted from the highly dispersed and increased basic sites (Mg-O2-). These findings hold promise for advancing efficient and environmentally friendly NO2 adsorption materials, critical for addressing the challenges posed by NO2-induced air pollution and safeguarding air quality.