Synthesis and physicochemical properties of silica gels with small additives of aluminium and zirconium ions

The method of synthesis of silica gels containing small additives of Al and Zr ions was developed. The porous structure of the synthesized Al,Zr-silica gels has been characterized by the adsorption method. It was found that simultaneous modification of silica gels by aluminium and zirconium ions lead to the formation of micro- and ultramicroporous samples in neutral media of precipitation. The parameters of porous structure of Al,Zr-silica gels are considerably dependent on the modified ions contents. A supposition was made that the formation of porous structure was caused by mutual stabilizing effect of Al and Zr additives on silica gel globules growth at sol-gel stages of synthesis. The nature of surface active sites of the modified silica gels was studied by the diffuse-reflectance IR-spectroscopy with the use of adsorption of deuteroacetonitrile

Ultramicroporous membranes for hydrogen separation

Fuel cell systems offer excellent efficiencies when compared to internal combustion engines, which result in reduced fuel consumption and greenhouse gas emissions. One of the areas requiring research for the success of fuel cell technology is the H2 fuel purification to reduce CO, which is a poison to fuel cells. Molecular sieve silica (MSS) membranes have a potential application in this area. In this work showed activated transport, a characteristic of ultramicroporous (d

Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql-SIFSIX-bpe-Zn exhibits an induced fit binding mechanism when exposed to acetylene, C₂H₂. The resulting phase change affords exceptionally strong C₂H₂ binding that in turn enables highly selective C₂H₂/C₂H₄ and C₂H₂/CO₂ separation demonstrated by dynamic breakthrough experiments. sql-SIFSIX-bpe-Zn was observed to exhibit at least four phases: as-synthesised (α); activated (β); and C₂H₂ induced phases (β' and γ). sql-SIFSIX-bpe-Zn-β exhibited strong affinity for C₂H₂ at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Qst ) of 67.5 kJ mol⁻¹ validated through in situ pressure gradient differential scanning calorimetry (PG-DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C₂H₂ induced fit transformation, binding positions and the nature of host-guest and guest-guest interactions

Enhanced resolution of ultra micropore size determination of biochars and activated carbons by dual gas analysis using N2 and CO2 with 2D-NLDFT adsorption models

International audienc

Highly Productive C₃H₄/C₃H₆ Trace Separation by a Packing Polymorph of a Layered Hybrid Ultramicroporous Material

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu, a new variant of a previously reported ultramicroporous square lattice, sql, topology material, sql-SIFSIX-bpe-Zn, can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA (AA) and sql-NbOFFIVE-bpe-Cu-AB (AB), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA (AA) is isostructural with sql-SIFSIX-bpe-Zn, each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB (AB) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C3H4/C3H6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C3H4/C3H6 selectivity (270) and a new benchmark for productivity (118 mmol g-1) of polymer grade C3H6 (purity &gt;99.99%) from a 1:99 C3H4/C3H6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot"for C3H4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C3H4 and C3H6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.</p

Structural‐Deformation‐Energy‐Modulation Strategy in a Soft Porous Coordination Polymer with an Interpenetrated Framework

German version: https://doi.org/10.1002/ange.202003186To achieve unique molecular‐recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (Edef) of soft PCPs and the guest interaction is key for selective a guest‐triggered structural‐transformation behavior. Therefore, it is vital to investigate and control Edef to regulate this competition for flexibility control. Driven by these theoretical insights, we demonstrate an Edef‐modulation strategy via encoding inter‐framework hydrogen bonds into a soft PCP with an interpenetrated structure. As a proof of this concept, the enhanced Edef of PCP enables a selective gate‐opening behavior toward CHCl₃ over CH₂Cl₂ by changing the adsorption‐energy landscape of the compounds. This study provides a new direction for the design of functional soft porous materials

Adsorbed Gas Behaviour and Guest-Host Interactions in Ultramicroporous Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous materials that have attracted much attention due to their large surface areas, high tunability and their high selectivity for gas adsorption applications. In this work, solid-state nuclear magnetic resonance (SSNMR) experiments and single crystal X-ray diffraction (SCXRD) experiments are used to investigate carbon dioxide adsorption within the ultramicroporous MOFs SIFSIX-3-Zn (Chapter 2) and ZnAtzOx. (Chapter 3). Analysis finds that the CO2 SIFSIX-3-Zn undergoes wobbling motions with a low temperature dependence, and in ZnAtzOx undergoes wobbling and hopping motions with a low temperature dependence. SCXRD is used to precisely determine the CO2 adsorption site in SIFSIX-3-Zn, centered within the pore. Chapter 4 discusses the use of SSNMR to study the effects of water adsorption within these MOFs, with preliminary results suggesting water is strongly adsorbed in both frameworks with a low degree of temperature dependence

Commensurate stacking within confined ultramicropores boosting acetylene storage capacity and separation efficiency

Developing advanced porous materials possessing both a high storage capacity and selectivity for acetylene (C2H2) remains challenging but a sought-after endeavor. Herein we show a strategy involving synergic combination of spatial confinement and commensurate stacking for enhanced C2H2 storage and capture via maximizing the host—guest and guest—guest interactions. Two ultramicroporous metal-organic frameworks (MOFs), MIL-160 and MOF-303 are elaborately constructed to exhibit ultrahigh C2H2 uptakes of 235 and 195 cm3·g−1, respectively, due to the confinement effect of the suitable pore sizes and periodically dispersed molecular recognition sites. Specially, C2H2 capacity of MIL-160 sets a new benchmark for C2H2 storage. The exceptional separation performances of two materials for C2H2 over both CO2 and ethylene (C2H4), which is rarely observed, outperform most of the benchmark materials for C2H2 capture. We scrutinized the origins of ultrahigh C2H2 loading in the confined channels via theoretical investigations. The superior separation efficiency for C2H2/CO2 and C2H2/C2H4 mixtures with unprecedented C2H2 trapping capacity (&gt; 200 L·kg−1) was further demonstrated by dynamic breakthrough experiments. </p