The role of ultramicropores in the CO2 adsorption capacity of Fe–BTC crystallites synthesized with a perturbation-assisted nanofusion synthesis strategy

Abstract

Herein, we report the highest BET surface area (1312 m² g⁻¹) and the highest total pore volume (1.41 cm³ g⁻¹) reported for Fe–BTC to date. More importantly, a CO₂ adsorption capacity of 27.5 wt% (6.24 mmol g⁻¹) is achieved at 8.5 bar and 298 K, which is the highest reported value for Fe–BTC to date. A perturbation-assisted nanofusion mechanism is used to synthesize Fe–BTCs, which form hierarchical pores. The synthesis parameters are optimized to enhance the amount of CO₂ adsorbed. The highest CO₂ adsorption capacity is achieved by Fe–BTC, which has ultramicropores (pore diameter <0.7 nm) in its pore structure. This measured CO₂ uptake capacity (1 bar and 298 K) is higher than those of the MOFs (MOF-177, UMCM-1, MIL-101(Cr), ZIF-8, and MOF-5) reported in the literature. Herein, we experimentally prove the significant contribution of ultramicropores and narrow micropores for the adsorbed CO₂ amount. In conclusion, this study i) reports a strategy that increases the BET surface area (1.6 times), total pore volume (3.1 times) and CO₂ adsorption capacity (1.66 times) and ii) shows the critical role of ultramicropores and the volume and distribution of narrow micropores on the adsorbed CO₂ amount. The reported synthesis strategy can lead the way for the synthesis of highly porous sorbents with an enhanced BET surface area, total pore volume and CO₂ sorption capacity, which should be further examined for other porous sorbents to achieve CO₂ sorption goals.