Novel M (Mg/Ni/Cu)-Al-CO₃ layered double hydroxides synthesized by aqueous miscible organic solvent treatment (AMOST) method for CO₂ capture

Layered double hydroxides (LDHs) have been intensively studied in recent years owing to their great potential in CO₂ capture. However, the severe aggregation between platelets and low surface area restricted it from exhibiting very high CO₂ adsorption capacity and CO₂/N₂ selectivity. In this research, we for the first time synthesized Ni-Al-CO₃ and Cu-Al-CO₃ LDHs using aqueous miscible organic solvent treatment (AMOST) method. The as-synthesized materials were evaluated for CO₂ adsorption at three different temperatures (50, 80, 120 °C) applicable to post-combustion CO₂ capture. Characterized with XRD, N₂ adsorption-desorption, TEM, EDX, and TGA, we found the newly synthesized Ni-Al-CO₃ LDH showed a nano-flower-like morphology comprising randomly oriented 2D nanoplatelets with both high surface area (249.45 m²/g) and pore volume (0.59 cc/g). Experimental results demonstrated that un-calcined Ni-Al-CO₃ LDH is superior in terms of CO₂ capture among the three LDHs, with a maximum CO₂ adsorption capacity of 0.87 mmol/g and the ideal CO₂/N₂ selectivity of 166 at 50 °C under 1200 mbar for typical flue gas CO₂/N₂ composition (CO₂:N₂ = 15:85, v/v). This is the first report of a delaminated Ni-Al-CO₃ LDH showing better CO₂ capture performance than the well-reported optimal Mg layered double hydroxide.