Chrysanthemum flower like silica with highly dispersed Cu nanoparticles as a high-performance NO₂ adsorbent

Atmospheric NO₂ removal is urgent and necessary due to its negative effects on the eco-system. Here we developed the chrysanthemum flower-like silica (KCC-1) loaded with highly dispersed copper nanoparticles for efficient NO₂ removal under ambient conditions. We carefully studied the NO₂ removal performance of Cu-KCC-1 materials with different copper loadings (0, 5, 10, and 15 wt%) and demonstrated the Cu⁰ nanoparticles (10 wt%) boosted the NO₂ removal capacity of KCC-1 by up to 51 times. KCC-1 loaded with 10 wt% of copper was verified to be the best-performing adsorbents, featuring an efficient NO₂ removal capacity of 3.63 mmol/g and a moderate NO release (11.3%), which was primarily attributed to the presence of Cu⁰ nanoparticles. The mechanistic study unveiled that the loaded Cu⁰ particles served as active adsorption sites for NO₂ molecules and reduced the NO₂ dissociation by covering the sites primarily responsible for NO₂ dissociation (i.e., oxygen vacancies). This work affords a promising adsorbent for NO₂ abatement under ambient conditions. The new knowledge established in developing adsorbents for NO₂ would promote future research in this emerging and niche area of air pollution control.