A Chemically Stable Hofmann-Type Metal-Organic Framework with Sandwich-Like Binding Sites for Benchmark Acetylene Capture.
basic_science · Level V
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- Also identified by DOI 10.1002/adma.201908275.
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Abstract
The realization of porous materials for highly selective separation of acetylene (C<sub>2</sub> H<sub>2</sub> ) from various other gases (e.g., carbon dioxide and ethylene) by adsorption is of prime importance but challenging in the petrochemical industry. Herein, a chemically stable Hofmann-type metal-organic framework (MOF), Co(pyz)[Ni(CN)<sub>4</sub> ] (termed as ZJU-74a), that features sandwich-like binding sites for benchmark C<sub>2</sub> H<sub>2</sub> capture and separation is reported. Gas sorption isotherms reveal that ZJU-74a exhibits by far the record C<sub>2</sub> H<sub>2</sub> capture capacity (49 cm<sup>3</sup> g<sup>-1</sup> at 0.01 bar and 296 K) and thus ultrahigh selectivity for C<sub>2</sub> H<sub>2</sub> /CO<sub>2</sub> (36.5), C<sub>2</sub> H<sub>2</sub> /C<sub>2</sub> H<sub>4</sub> (24.2), and C<sub>2</sub> H<sub>2</sub> /CH<sub>4</sub> (1312.9) separation at ambient conditions, respectively, of which the C<sub>2</sub> H<sub>2</sub> /CO<sub>2</sub> selectivity is the highest among all the robust MOFs reported so far. Theoretical calculations indicate that the oppositely adjacent nickel(II) centers together with cyanide groups from different layers in ZJU-74a can construct a sandwich-type adsorption site to offer dually strong and cooperative interactions for the C<sub>2</sub> H<sub>2</sub> molecule, thus leading to its ultrahigh C<sub>2</sub> H<sub>2</sub> capture capacity and selectivities. The exceptional separation performance of ZJU-74a is confirmed by both simulated and experimental breakthrough curves for 50/50 (v/v) C<sub>2</sub> H<sub>2</sub> /CO<sub>2</sub> , 1/99 C<sub>2</sub> H<sub>2</sub> /C<sub>2</sub> H<sub>4</sub> , and 50/50 C<sub>2</sub> H<sub>2</sub> /CH<sub>4</sub> mixtures under ambient conditions.