Cationic Polymer Used to Capture Zeolite Precursor Particles for the Facile Synthesis of Oriented Zeolite LTA Molecular Sieve Membrane

Cationic Polymer Used to Capture Zeolite Precursor Particles for the Facile Synthesis of Oriented Zeolite LTA Molecular Sieve Membran

Steam-Stable Zeolitic Imidazolate Framework ZIF-90 Membrane with Hydrogen Selectivity through Covalent Functionalization

A novel covalent functionalization strategy was developed to prepare reproducible ZIF-90 molecular sieve membranes by using 3-aminopropyltriethoxysilane as a covalent linker between the ZIF-90 layer and Al2O3 support via imines condensation. The ZIF-90 membranes show high thermal and hydrothermal stabilities, and they allow the separation of hydrogen from larger gases by molecular sieving

Functionalized Metal–Organic Framework UiO-66-NH-BQB for Selective Detection of Hydrogen Sulfide and Cysteine

Hydrogen sulfide (H2S) is an important signaling molecule related to many diseases. Thus, H2S has a great impact on the pathological and physiological processes in biological systems. Cysteine (l-Cys) is a building block for proteins and important metabolites. To understand their roles in the physiological metabolic procedures, the measurement of the H2S level and identifying cysteine in the biological system is significant. In this study, through the functionalization of UiO-66-NH2 by 4-(2,2-dicyanoethenyl)­benzoic acid (BQB), a novel UiO-66-NH-BQB is successfully synthesized and used as a fluorescence probe to recognize and detect H2S and l-Cys. The fluorescence signals of the probe are enhanced great when it is exposed to H2S or cysteine molecules; thus, it is able to determine quantificationally the H2S concentration in an aqueous solution. The detection limitation of the UiO-66-NH-BQB to H2S concentration is found to be as low as 1.74 μM. The developed fluorescent probe based on UiO-66-NH-BQB displays a high selectivity and excellent biocompatibility, which is very promising for recognition and sensing of biothiols in organisms

Bio-Inspired Polydopamine: A Versatile and Powerful Platform for Covalent Synthesis of Molecular Sieve Membranes

Inspired by the bioadhesive ability of the marine mussel, a simple, versatile, and powerful synthesis strategy was developed to prepare highly reproducible and permselective molecular sieve membranes by using polydopamine as a novel covalent linker. Attributing to the formation of strong covalent and noncovalent bonds, ZIF-8 nutrients are attracted and bound to the support surface, thus promoting the ZIF-8 nucleation and the growth of uniform, well intergrown, and phase-pure ZIF-8 molecular sieve membranes. The developed ZIF-8 membranes show high hydrogen selectivity and thermal stability. At 150 °C and 1 bar, the mixture separation factors of H₂/CO₂, H₂/N₂, H₂/CH₄, and H₂/C₃H₈ are 8.9, 16.2, 31.5 and 712.6, with H₂ permeances higher than 1.8 × 10^–7 mol·m^–2·s^–1·Pa^–1, which is promising for hydrogen separation and purification

Bicontinuous Zeolitic Imidazolate Framework ZIF-8@GO Membrane with Enhanced Hydrogen Selectivity

Through layer-by-layer (LBL) deposition of a graphene oxide (GO) suspension on a semicontinuous ZIF-8 layer, we have developed a novel bicontinuous ZIF-8@GO membrane. Since only the gaps between the ZIF-8 crystals are sealed by the GO layer due to capillary forces and covalent bonds, the gas molecules can only permeate through the ZIF-8 micropore system (0.34 nm). Therefore, the ZIF-8@GO membranes show high hydrogen selectivity. At 250 °C and 1 bar, the mixture separation factors of H2/CO2, H2/N2, H2/CH4, and H2/C3H8 are 14.9, 90.5, 139.1, and 3816.6, with H2 permeances of about 1.3 × 10–7 mol·m–2·s–1·Pa–1, which is promising for hydrogen separation and purification by molecular sieving

Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO₄) Molecular Sieve Membrane with High Hydrogen Permselectivity

Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO4) Molecular Sieve Membrane with High Hydrogen Permselectivit

Monitoring Molecular Mass Transfer in Cation-Free Nanoporous Host Crystals of Type AlPO-LTA

Micro-imaging is employed to monitor the evolution of intra-crystalline guest profiles during molecular adsorption and desorption in cation-free zeolites AlPO-LTA. The measurements are shown to provide direct evidence on the rate of intra-crystalline diffusion and surface permeation and their inter-relation. Complemented by PFG NMR and integral IR measurements, a comprehensive overview of the diffusivities of light hydrocarbons in this important type of host materials is provided

User-Tailored Metal–Organic Frameworks as Supports for Carbonic Anhydrase

Carbonic anhydrase (CA) was previously proposed as a green alternative for biomineralization of carbon dioxide (CO2). However, enzyme’s fragile nature when in synthetic environment significantly limits such industrial application. Herein, we hypothesized that CA immobilization onto flexible and hydrated “bridges” that ensure proton-transfer at their interfaces leads to improved activity and kinetic behavior and potentially increases enzyme’s feasibility for industrial implementation. Our hypothesis was formulated considering that water plays a key role in the CO2 hydration process and acts as both the reactant as well as the rate-limiting step of the CO2 capture and transformation process. To demonstrate our hypothesis, two types of user-synthesized organic metallic frameworks [metal–organic frameworks (MOFs), one hydrophilic and one hydrophobic] were considered as model supports and their surface characteristics (i.e., charge, shape, curvature, size, etc.) and influence on the immobilized enzyme’s behavior were evaluated. Morphology, crystallinity and particle size, and surface area of the model supports were determined by scanning electron microscopy, dynamic light scattering, and nitrogen adsorption/desorption measurements, respectively. Enzyme activity, kinetics, and stability at the supports interfaces were determined using spectroscopical analyses. Analysis showed that enzyme functionality is dependent on the support used in the immobilization process, with the enzyme immobilized onto the hydrophilic support retaining 72% activity of the free CA, when compared with that immobilized onto the hydrophobic one that only retained about 28% activity. Both CA–MOF conjugates showed good storage stability relative to the free enzyme in solution, with CA immobilized at the hydrophilic support also revealing increased thermal stability and retention of almost all original enzyme activity even after heating treatment at 70 °C. In contrast, free CA lost almost half of its original activity when subject to the same conditions. This present work suggests that MOFs tunable hydration conditions allow high enzyme activity and stability retention. Such results are expected to impact CO2 storage and transformation strategies based on CA and potentially increase user-integration of enzyme-based green technologies in mitigating global warming