As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.

Effective capture of radioactive organic iodides from nuclear waste remains a significant challenge due to the drawbacks of current adsorbents such as low uptake capacity, high cost, and non-recyclability. We report here a general approach to overcome this challenge by creating radioactive organic iodide molecular traps through functionalization of metal-organic framework materials with tertiary amine-binding sites. The molecular trap exhibits a high CH3I saturation uptake capacity of 71 wt% at 150 °C, which is more than 340% higher than the industrial adsorbent Ag0@MOR under identical conditions. These functionalized metal-organic frameworks also serve as good adsorbents at low temperatures. Furthermore, the resulting adsorbent can be recycled multiple times without loss of capacity, making recyclability a reality. In combination with its chemical and thermal stability, high capture efficiency and low cost, the adsorbent demonstrates promise for industrial radioactive organic iodides capture from nuclear waste. The capture mechanism was investigated by experimental and theoretical methods.

Inorganic semiconductor materials are best known for their superior physical properties, as well as their structural rigidity and stability. However, the poor solubility and solution-processability of these covalently bonded network structures has long been a serious drawback that limits their use in many important applications. Here, we present a unique and general approach to synthesize robust, solution-processable, and highly luminescent hybrid materials built on periodic and infinite inorganic modules. Structure analysis confirms that all compounds are composed of one-dimensional anionic chains of copper iodide (Cu m I m+2 2–) coordinated to cationic organic ligands via Cu–N bonds. The choice of ligands plays an important role in the coordination mode (μ1-MC or μ2-DC) and Cu–N bond strength. Greatly suppressed nonradiative decay is achieved for the μ2-DC structures. Record high quantum yields of 85% (λex = 360 nm) and 76% (λex = 450 nm) are obtained for an orange-emitting 1D-Cu4I6(L 6). Temperature dependent PL measurements suggest that both phosphorescence and thermally activated delayed fluorescence contribute to the emission of these 1D-AIO compounds, and that the extent of nonradiative decay of the μ2-DC structures is much less than that of the μ1-DC structures. More significantly, all compounds are remarkably soluble in polar aprotic solvents, distinctly different from previously reported CuI based hybrid materials made of charge-neutral Cu m X m (X = Cl, Br, I), which are totally insoluble in all common solvents. The greatly enhanced solubility is a result of incorporation of ionic bonds into extended covalent/coordinate network structures, making it possible to fabricate large scale thin films by solution processes.

Flexible metal−organic frameworks (MOFs) hold great promise as smart materials for specific applications such as gas separation. These materials undergo interesting structural changes in response to guest molecules, which is often associated with unique adsorption behavior not possible for rigid MOFs. Understanding the dynamic behavior of flexible MOFs is crucial yet challenging as it involves weak host−guest interactions and subtle structural transformation not only at the atomic/molecular level but also in a nonsteady state. We report here an in-depth study on the adsorbate-and temperature-dependent adsorption in a flexible MOF by crystallizing atomic gases into its pores. Mn(ina) 2 shows an interesting temperature-dependent response toward noble gases. Its nonmonotonic, temperature-dependent adsorption profile results in an uptake maximum at a temperature threshold, a phenomenon that is unusual. Full characterization of Xe-loaded MOF structures is performed by in situ singlecrystal and synchrotron X-ray diffraction, IR spectroscopy, and molecular modeling. The X-ray diffraction analysis offers a detailed explanation into the dynamic structural transformation and provides a convincing rationalization of the unique adsorption behavior at the molecular scale. The guest and temperature dependence of the structural breathing gives rise to an intriguing reverse of Xe/Kr adsorption selectivity as a function of temperature. The presented work may provide further understanding of the adsorption behavior of noble gases in flexible MOF structures.

Hydrolytically stable adsorbents are needed for water vapor sorption related applications; however, design principles for porous materials with tunable water sorption behavior are not yet established. Here, we report that a platform of fourth-generation metal-organic materials (MOMs) with rigid frameworks and self-switching pores can adapt their pores to modulate water sorption. This platform is based upon the hydrolytically stable material CMOM-3S, which exhibits bnn topology and is composed of rod building blocks based upon S-mandelate ligands, 4,4-bipyridine ligands, and extraframework triflate anions. Isostructural variants of CMOM-3S were prepared using substituted R-mandelate ligands and exhibit diverse water vapor uptakes (20-67 cm/g) and pore filling pressures ( P/ P, 0.55-0.75). [Co( R-4-Cl-man)(bpy)](OTf) (33R) is of particular interest because of its unusual isotherm. Insight into the different water sorption properties of the materials studied was gained from analysis of in situ vibrational spectra, which indicate self-switching pores via perturbation of extraframework triflate anions and mandelate linker ligands to generate distinctive water binding sites. Water vapor adsorption was studied using in situ differential spectra that reveal gradual singlet water occupancy followed by aggregation of water clusters in the channels upon increasing pressure. First-principles calculations identified the water binding sites and provide structural insight on how adsorbed water molecules affect the structures and the binding sites. Stronger triflate hydrogen bonding to the framework along with significant charge redistribution were determined for water binding in 33R. This study provides insight into a new class of fourth-generation (self-switching pores) MOM and the resulting effect upon water vapor sorption properties.