Adsorptive separation of propylene/propane (C3H6/C3H8) mixture is desired for its potential energy saving on replacing currently deployed and energy‐intensive cryogenic distillation. Realizing efficient C3H6/C3H8 separation in the emerging hydrogen‐bonded organic frameworks (HOFs) is very challenging owing to the lack of functional sites for preferential gas binding. By virtue of crystal engineering, we herein report a functionalized HOF (HOF‐16) with free ‐COOH sites for the efficient separation of C3H6/C3H8 mixtures. Under ambient conditions, HOF‐16 shows a significant C3H6/C3H8 uptake difference (by 76 %) and selectivity (5.4) in contrast to other carboxylic acid‐based HOFs. Modeling studies indicate that free ‐COOH groups together with the suitable pore confinement facilitate the recognition and high‐density packing of gas molecules. The separation performance of HOF‐16 was validated by breakthrough experiments. HOF‐16 is stable towards strong acidity and water.

No abstract

Coexistence of multiferroic orders attached increasing attentions on its potential applications in multiple-state memory, switch, and computing, but it is still challenging to design the single-phase crystalline materials hosting multiferroic...

Switching materials in channels of nonlinear optics (NLOs) are of particular interest in NLO material science. Numerous crystalline NLO switches based on structural phase transition have emerged, but most of them reveal asingle-step switch between two different second-harmonic-generation (SHG) states,a nd only very rare cases involve three or more SHG states.Herein, we report anew organic-inorganic hybrid salt, (Me 3 NNH 2 ) 2 [CdI 4 ], which is an unprecedented case of ar eversible three-step NLO switch between SHG-silent, -medium, -low,a nd -high states,w ith high contrasts of 25.5/ 4.3/9.2 in at emperature range of 213-303 K. By using the combined techniques of variable-temperature X-rays inglecrystal structural analyses,d ielectric constants,s olid-state 13 C nuclear magnetic resonance spectroscopy, and Hirshfeld surface analyses,w ed isclose that this four-state switchable SHG behavior is highly associated with the stepwise-changed molecular dynamics of the polar organic cations.This finding demonstrates well the complexity of molecular dynamics in simple hybrid salts and their potential in designing new advanced multistep switching materials.

Porous molecular crystals sustained by hydrogen bonds and/or weaker connections are an intriguing type of adsorbents,b ut they rarely demonstrate efficient adsorptive separation because of poor structural robustness and tailorability.Herein, we report aporous molecular crystal based on hydrogen-bonded cyclic dinuclear Ag I complex, whichexhibits exceptional hydrophobicity with awater contact angle of 1348 8, and high chemical stability in water at pH 2-13. The seemingly rigid adsorbent shows apore-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.I nsitu powder/single-crystal X-rayd iffraction and computational simulations reveal that at rivial guest-induced structural transformation playsac ritical role.