NO2 Removal by Adsorption on Transition-Metal-Based Layered Double Hydroxides

The emission of nitrogen dioxide (NO 2 ) has caused severe air pollution and threatened the safety of the environment and people’s health. Various techniques have been intensively explored for the abatement of NO 2, mostly on the basis of catalytic reduction at elevated temperature, but few have shown satisfactory NO 2 removal efficiency at ambient conditions. The use of solid porous adsorbents is a promising approach for NO 2 removal due to their high capacity and low energy penalty for regeneration. Here, we report the uncalcined transition-metal-based layered double hydroxides (TM–Al–CO 3 LDHs) as ambient NO 2 adsorbents. The dynamic breakthrough experiments demonstrated that Ni–Al–CO 3 LDH showed a superior NO 2 adsorption capacity above 5.3 mmol g –1 and the lowest NO generation ratio (∼31.7% of the total NO 2 input) among the four TM–Al–CO 3 adsorbents. The in situ diffuse reflectance infrared Fourier transform spectroscopy disclosed the reactive adsorption mechanism between NO 2 and LDHs via acid–base interaction. The reversibility of active adsorption sites in Ni–Al–CO 3 LDH could maintain over 74% after six adsorption–desorption cycles, suggesting a decent regenerability of Ni–Al–CO 3 as the NO 2 adsorbent.