Low Temperature CO₂ Methanation: ZIF-67-Derived Co-Based Porous Carbon Catalysts with Controlled Crystal Morphology and Size

A Co-based zeolitic imidazolate framework, ZIF-67, has been utilized as a precursor to obtain Co-based porous carbon catalysts. The obtained catalysts display an outstanding catalytic performance toward the CO₂ methanation at low temperature. The ZIF-67 crystal morphology can be controlled from cubic to rhombic dodecahedron, and the original particle sizes can be regulated from 150 nm to 1 μm in aqueous solution by cetyltrimethylammonium bromide (CTAB) surfactants. After carbonation in N₂ flow, Co-based porous carbon catalysts kept the original ZIF-67 crystal morphology and particle size but differed in the micropore property; the 0.01 wt % CTAB content led to the maximum micropore volume 0.125 cm³/g. The Co nanoparticles inside the carbon matrix range between 7 and 20 nm, and they are separated by the graphite-like carbon avoiding the metal sintering effectively. Furthermore, the catalysts with 0.01% CTAB addition exhibited the highest CO₂ conversion (52.5%) and CH₄ selectivity (99.2%) under the 72000 mL g^-1 h^-1 GHSV (gas hourly space velocity) at 270 °C. Noticeably, the Co/PC catalysts performed higher activity and stability than the supported catalysts 20Co/AC. The versatile way offers good prospects for low temperature CO₂ methanation and prevents metal sintering effectively.