Selective Capture of Carbon Dioxide from Hydrocarbons Using a Metal-Organic Framework: Relevance to the Purification of Natural Gas and Acetylene
<p>Efficient and sustainable methods for carbon dioxide (CO<sub>2</sub>) capture are highly sought after. Mature technologies involve chemical reactions that absorb CO<sub>2, </sub>but they have many drawbacks. Energy-efficient alternatives may be realized by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO<sub>2</sub>. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16 (MUF = Massey University Framework). This metal-organic framework captures CO<sub>2</sub> with a high affinity in its one-dimensional channels. The position of the CO<sub>2</sub> molecules sequestered in the framework pores, as determined by X-ray crystallography, illustrate how complementary noncovalent interactions envelop the CO<sub>2</sub> while repelling other guest molecules. The low affinity of the MUF-16 pores for these competing gases underpins new benchmarks for the adsorption of CO<sub>2</sub> over methane, acetylene, ethylene, ethane, propylene and propane. IAST calculations show that for 50/50 mixtures at 293 K and 1 bar, the CO<sub>2</sub>/CH<sub>4</sub> selectivity is 6690 and the CO<sub>2</sub>/C<sub>2</sub>H<sub>2</sub> selectivity is 510, for example. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products. Ultimately, MUF-16 may be applicable to the removal of CO<sub>2 </sub>from sources such as natural gas and chemical feedstocks.<br></p>