A Hydrogen-Bonded yet Hydrophobic Porous Molecular Crystal for Molecular-Sieving-like Separation of Butane and Isobutane.

Porous molecular crystals sustained by hydrogen bonds and/or weaker connections are an intriguing type of adsorbents, but they hardly demonstrate efficient adsorptive separation becuase of poor structural robustness and tailorability. Here, we report a porous molecular crystal based on hydrogen-bonded cyclic dinuclear Ag(I) complex, which exhibits exceptional hydrophobicity with a water contact angle of 134 o , high chemical stability in water at pH 2-13. The seemingly rigid adsorbent shows pore-opening or nonporous-to-porous type butane adsorption isotherm and complete exclusion of isobutane, indicating potential molecular sieving. Quantitative column breakthrough experiments show slight co-adsorption of isobutane with an experimental butane/isobutane selectivity of 23, and isobutane can be purified more efficiently than for butane. In-situ powder/single-crystal X-ray diffraction and computational simulations reveal that a trivial guest-induced structural transformation play critical roles.