High and selective CO2 uptake, H2storage and methanol sensing on the amine-decorated 12-connected MOF CAU-1

Abstract

The amine-decorated microporous metal–organic framework CAU-1 was readily synthesized and activated using a home-made efficient protocol. It exhibited a high heat of adsorption for CO₂, high CO₂ uptake capacity, and an impressive selectivity for CO₂ over N₂. At 273 K and up to 1 atm, CO₂ uptake capacity can reach as much as 7.2 mmol g⁻¹. Comparatively, the CH₄ and N₂ uptakes at 273 K and 1 atm were only 1.34 mmol g⁻¹ and 0.37 mmol g⁻¹, respectively. The CO₂/N₂ selectivity was 101 : 1 at 273 K. The isosteric heat of adsorption (Q_st) for CO₂ was ∼48 kJ mol⁻¹ at the onset of adsorption, and it decreases to ∼28 kJ mol⁻¹ at higher CO₂ pressures. Furthermore, CAU-1 can adsorb 2.0 wt% and 4.0 wt% hydrogen at 77 K under 1 atm and 30 atm, respectively. The adsorption characteristics of CAU-1 for methanol investigated in situ with a quartz crystal microbalance (QCM), indicated that this particular MOF structure can be used as a highly sensitive sensor for methanol detection such as direct methanol fuel cells.