Mesoporous silica SBA-15 modified with copper as an efficient NO2 adsorbent at ambient conditions

Copper oxide particles were synthesized by precipitation in sodium hydroxide and dispersed simultaneously in mesoporous SBA-15 silica. The materials were then submitted to thermal treatment under nitrogen at different temperatures. They were tested as novel NO2 adsorbents in dynamic condition at room temperature. The surface of the initial and exhausted materials was characterized using N2 adsorption, XRD, TEM, thermal analysis and FT-IR. The addition of Cu2O particles leads to a significant increase in the NO2 adsorption capacity. However, no trend between the NO2 capacity and the temperature of the thermal treatment of the materials has been observed. The amount of NO released during the NO2 adsorption was found to be lower on the materials submitted to a low temperature treatment. On these materials, the formation of copper nitrites is favored, whereas on materials treated at higher temperature, copper nitrates are formed as a predominant species. The results suggest that silanol groups of the silica matrix play an important role in NO2 adsorption and NO retention at room temperature.

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► Copper oxide particles were dispersed in mesoporous silica SBA-15.
► Composite materials show higher NO2 adsorption capacities than SBA-15.
► The density of silanol groups on the surface of the silica is affected by the thermal post-treatment.
► Both copper oxide particles and silanol groups are active centers for NOx retention.
► A better retention of NO is observed on the silica surface with high density of silanol groups.