Unveiling the sequential CO2/CH4 activation process on Co3O4 nanoparticles encapsulated by mesoporous silica shell

The sequential activation of CO2 and CH4 on metal oxides enables the formation of various oxygenated compounds, i.e., CH3COOH, CH3OH, CH3CHO, and CH3COCH3. This study focuses on elucidating the activation processes on Co3O4 nanoparticles encapsulated by mesoporous silica shell (nCo(3)O(4)@mSiO(2)). Comprehensive characterization techniques are employed to unveil the activation processes, with optimizing activation conditions to maximize product yield. In sole activation experiments, CO2 is absorbed on the metal oxide, forming a carbonate structure that desorbs reversibly depending on temperature. Additionally, nCo(3)O(4)@mSiO(2) activates CH4 through C-H bond cleavage, stabilizing as Co-CH3* species with O-H* species on the oxide framework. Sequential activation processes using nCo(3)O(4)@mSiO(2) result in carboxylative or carbonylative coupling of CO2 or CO released from the metal carbonate surface with CH4, yielding CH3COOH or CH3CHO, respectively. CH3OH production is achievable by altering the activation sequence. Post-extraction enables collection of adsorbed oxygenated products, allowing for nCo(3)O(4)@mSiO(2) reuse without altering product yield.