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Designing zeolites with tunable physicochemical properties can substantially impact their performance in commercial applications, such as adsorption, separations, catalysis, and drug delivery. Zeolite synthesis typically requires an organic structure-directing agent to produce crystals with specific pore topology. Attempts to remove organics from syntheses to achieve commercially viable methods of preparing zeolites often lead to the formation of impurities. Herein, we present organic-free syntheses of two polymorphs of the small-pore zeolite P (GIS), P1 and P2. Using a combination of adsorption measurements and density functional theory calculations, we show that GIS polymorphs are selective adsorbents for H2O relative to other light gases (e.g., H2, N2, CO2). Our findings refute prior theoretical studies postulating that GIS-type zeolites are excellent materials for CO2 separation/sequestration. We also show that P2 is significantly more thermally stable than P1, which broadens the operating conditions for GIS-type zeolites in commercial applications and opens new avenues for exploring their potential use in processes such as catalysis. [ABSTRACT FROM AUTHOR]

A flexible metal–organic framework constructed from a flexible linker is shown to possess the capability of separating mixtures of polar compounds (propanol isomers) by exploiting the differences in the saturation capacities of the constituents. Transient breakthrough simulations show that these sorption-based separations are in favor of the component with higher saturation capacity. [ABSTRACT FROM AUTHOR]

New approaches to tailor the synthesis of zeolite polymorphs can lead to breakthroughs in applications spanning from separations to adsorption. A comparison of small ‐ pore zeolite GIS polymorphs P1 and P2 revealed marked differences in their thermal stability. Moreover, adsorption experiments and DFT studies collectively showed that GIS polymorphs are promising materials for selective separation of small molecules. More information can be found in the Full Paper by R. K. Motkuri, J. D. Rimer et al. on page 16078 ff. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are one of the widely investigated materials of 21st century due to their unique properties such as structural tailorability, controlled porosity, and crystallinity. These exceptional properties make them promising candidates for various applications including gas adsorption and storage, separation, and catalysis. However, commercial applications of MOFs produced by conventional methods including solvothermal or hydrothermal synthesis are rather limited or restricted because they often produce fine powders. The use of MOF powders for industrial applications often results in pressure drop problems similar to the case with zeolites and limited robustness against water. To realize these materials for practical applications, densification of MOFs (by increasing pellet density) is routinely employed to form pellets, extrudates or beads to improve the overall density, volumetric adsorption, mechanical and thermal properties. However, the improvements come with some drawbacks such as reduction in overall porosity, surface area, and gravimetric adsorption capacity. Thus, optimizing the properties of densified MOF's by tuning the pellet density is very crucial for realizing these materials for industrial applications. Methods that increase the packing density in MOFs (for example by intentional interpenetration, etc.), which is different from pellet density, is not the scope of this review. In this review, the properties and applications of densified MOFs with different metal clusters and organic linkers are discussed. [ABSTRACT FROM AUTHOR]