Multiple space from the interior of metal-organic polyhedra (MOPs), the exterior among MOPs, and the inherent nature of big organic molecules makes MOPs as promising platform with hierarchical porous structures, especially when well-elucidated reticular chemistry principles were used. Herein we describe the preparation of a series of isoreticular octahedral MOPs featuring Zn₄-p-tert-butylsulfonylcalix[4]arene clusters by the metal-directed assembly of three rigid organic ligands with different lengths. Intercage hydrogen-bonds and hydrophobic interactions between sulfonylcalix[4]arene groups direct the stacking of discrete MOPs into a novel permanent hierarchical porous material. More importantly, the optimal MOP 1-Zn exhibits high adsorption capacity of Xe and excellent Xe/Kr (20/80, v/v) separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. Additionally, grand canonical Monte Carlo (GCMC) and dispersion-corrected density functional theory (DFT-D) theoretical calculations provide molecular-level insight over the adsorption/separation mechanism.

Separation of propane from natural gas is of great importance to industry. However, in light of size-based separation, there still lacks effective method to directly separate propane from natural gas, due to the comparable physical properties for these light alkanes (C1–C4) and the middle size of propane. In this work, we found that a new Th-metal-organic framework (MOF) could be an ideal solution for this issue. The Th-MOF takes UiO-66-type structure, but with the pocket sealed by six-fold imide groups; this not only precisely reduces the size of pocket to exactly match propane, but also enhances the host–guest interactions through multiple (C)H(^δ+)∙∙∙(^δ−)O(C) interactions. As a result, highly selective adsorption of propane over methane, ethane, and butane was observed, implying unique middle-size separation. The actual separation was confirmed by breakthrough experiments of simulated natural gas, confirming its superior application in direct separation of propane from natural gas. The separation mechanism, as unveiled by both theoretical calculation and comparative experiments, is due to the six-fold imide-sealed pocket that could effectively distinguish propane from other light alkanes through both size effect and host–guest interactions.

The reticular chemistry strategy presents a powerful molecule-design tool to tailor the physical and chemical properties of metal–organic framework (MOF). In this work, we for the first time investigated the effect of organic ligands on the radionuclide sequestration (TcO₄⁻) of thorium–organic framework. Through a coordination modulation technique, two novel isoreticular thorium–organic frameworks, namely Th-MOF-67 and Th-MOF-68, were obtained. Relative to the antetype MOF of Th-MOF-66 that shows extremely low uptake of ReO₄⁻ (a chemical surrogate of radioactive TcO₄⁻), the isoreticular MOFs of Th-MOF-67 and Th-MOF-68 enable ultrahigh uptake of ReO₄⁻, giving an impressively 36.8-fold or 56-fold enhancement, respectively. The adsorption capacity of Th-MOF-68 is as high as 560 mg/g, exceeding most reported adsorbents for such use. The mechanism for such exceptional outstanding performance, as unveiled by both the single crystal X-ray diffraction and theoretical calculation, is due to coordination interaction for Th-MOF-67, when a tetrazolate ligand was used, or a combined effect from both coordination interaction and anion-exchange for Th-MOF-68, if using a triazolate ligand.