CO2 adsorption and catalytic application of Co-MOF-74 synthesized by microwave heating

Abstract

High-quality Co-MOF-74 crystals were successfully synthesized in 1h by microwave heating (Co-MOF-74(M)). The XRD pattern and textural properties of Co-MOF-74(M) including the BET surface area (1314m2g−1) were virtually identical to those of a sample synthesized in 24h by the solvothermal method (Co-MOF-74(S), 1327m2g−1). Average particle size of the former (ca. 50μm long and 8μm wide) was, however, significantly smaller than that of the latter (ca. 300μm long and 70μm wide). The H2O adsorption capacities of the crystals at 25°C were 466 and 605mgg−1 for Co-MOF-74(M) and Co-MOF-74(S), respectively. The adsorption isotherms of Co-MOF-74(M) for CO2 and N2 showed a high CO2 adsorption capacity (288mgg−1) and excellent selectivity over N2 (>25:1) at 25°C. Eight consecutive adsorption–desorption cycles established that there was no deterioration in the adsorption capacity, which showed reversible adsorbent regeneration at 100°C under He flow for a total duration of 1100min. Co-MOF-74(M) also demonstrated excellent catalytic performance in cycloaddition of CO2 to styrene oxide under relatively mild reaction conditions (2.0MPa, 100°C) with close to 100% selectivity to carbonate confirmed by GC–MS, 1H NMR, and FT-IR. Styrene oxide conversion increased with CO2 pressure and reaction temperature. No appreciable effect of catalyst particle size was detected, and Co-MOF-74(M) could be reused 3 times without loss of catalytic activity and with no structural deterioration.