A Chemically Stable Hofmann-Type Metal-Organic Framework with Sandwich-Like Binding Sites for Benchmark Acetylene Capture.

The realization of porous materials for highly selective separation of acetylene (C H ) 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) ] (termed as ZJU-74a), that features sandwich-like binding sites for benchmark C H capture and separation is reported. Gas sorption isotherms reveal that ZJU-74a exhibits by far the record C H capture capacity (49 cm g at 0.01 bar and 296 K) and thus ultrahigh selectivity for C H /CO (36.5), C H /C H (24.2), and C H /CH (1312.9) separation at ambient conditions, respectively, of which the C H /CO 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 H molecule, thus leading to its ultrahigh C H 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 H /CO , 1/99 C H /C H , and 50/50 C H /CH mixtures under ambient conditions.