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Graphical abstract:

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 Al2O3support 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.

The removal of heavy-metal ions from wastewater has drawn intense attention, because of their toxicity, bioaccumulation tendency, and persistency in nature. Adsorption is regarded as one of the most promising methods, because of its simplicity and efficiency. In the present work, we report the preparation of a novel EDTA-functionalized covalent organic framework (COF) for the removal of heavy-metal ions. First, a COF named TpPa-NO2was reduced to TpPa-NH2by using Na2S2O4as a reductant, and then EDTA dianhydride was grafted onto TpPa-NH2to obtain TpPa-NH2@EDTA through post-modification. Both the COF morphology and structure remained unchanged after post-modification. The TpPa-NH2@EDTA showed excellent performance in adsorbing different types of heavy-metal ions, such as soft Lewis acid (Ag+, Pd2+), hard Lewis acid (Fe3+, Cr3+), and borderline Lewis acid (Cu2+, Ni2+), and the removal efficiencies are all >85% within 5 min, because of the strong chelation effect of EDTA. The TpPa-NH2@EDTA also showed high adsorption ability in a pH ≥3 environment and have an adsorption capacity of >50 mg/g for the six representative heavy-metal ions. This work provides a new idea for the application of COF materials in the removal of heavy-metal ions from wastewater.

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-NH2by 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.

Thin, well-intergrown and phase-pure zeolite LTA membranes are prepared on the polyethyleneimine (PEI) modified substrates without seeding. For separation of 90.0 wt% iso-propanol/water mixtures by pervaporation, the LTA membrane shows a high separation performance, with a high separation factor of 44991 and water flux of 1.73 kg m-2 h-1at 90 °C.

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 CO2hydration process and acts as both the reactant as well as the rate-limiting step of the CO2capture 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 CO2storage and transformation strategies based on CA and potentially increase user-integration of enzyme-based green technologies in mitigating global warming.

Phase-pure and well-intergrown Cu-LTA membranes are developed through copper ions exchange of sodium ions in Na-LTA framework. For pervaporation of 90.0 wt% ethanol/10.0 wt% water mixtures, the Cu-LTA membrane shows much higher water flux than Na-LTA membranes due to the enhancement of the pore size after ions exchange.

Catalytic membrane reactors have the advantages of allowing the selective removal of products, avoiding the separation procedure of powder catalysts from the reaction mixture, intensifying the diffusion of reactants in the catalytic region, and integrating different reactions in one unit. Catalytic membrane reactors have been widely applied in the fields related to carbon peaking and carbon neutrality, including the capture and utilization of carbon dioxide, hydrogen production, and hydrogenation reaction. This review summarizes the design and fabrication of catalytic membrane reactors, with the focus on the capture and efficient utilization of carbon dioxide, hydrogen production and efficient liquid-phase hydrogenation. The design of membrane materials, catalyst materials and catalytic membranes, and the operation of catalytic membrane reactors are discussed respectively. Finally, the perspectives and future challenges of catalytic membrane reactors for carbon peaking and carbon neutrality are forecasted.

Engere Poren – mehr Selektivität: Die kovalente Modifizierung einer ZIF‐90‐Membran durch Iminkondensation von Ethanolamin mit der Aldehydgruppe des MOF‐Linkers (siehe Bild) führt zu engeren Membranporen, vermindert die nichtselektive Permeation durch Defektporen und verbessert dadurch das Molekularsiebverhalten. Für ein H2/CO2‐Gemisch konnte der Trennfaktor zwischen 7.3 und 62.5 eingestellt werden.

MOF constrictor: Covalent modification of a ZIF‐90 membrane was achieved by imine condensation of the aldehyde groups of the metal–organic framework (MOF) linker by ethanolamine (see picture). The modification leads to constriction of the pore apertures and prevents unselective permeation through defect pores, thus improving gas separation performance. For a H2/CO2mixture, selectivity can be increased from 7.3 to 62.5.

No Abstract

Hohe Wasserstoffselektivitätund thermische Stabilität zeichnen eine Membran des zeolithischen Imidazolats ZIF‐22 aus, die mithilfe des kovalenten Linkers 3‐Aminopropyltriethoxysilan (APTES) auf porösen keramischen Trägern abgeschieden wurde (siehe Bild). Bei 323 K wurden eine H2/CO2‐Selektivität von 7.2 und eine H2‐Durchlässigkeit von 1.6×10−7mol m−2s−1Pa−1erreicht.

Mono-, di-, and trimethylamine are the products of the successive methylation of ammonia. Using narrow-pore acidic catalysts of the CHA family like H-SAPO-34 or H-SSZ-13, the formation of the thermodynamically but bulky trimethylamine can be suppressed due to steric effects; thus, methylation is stopped at dimethylamine. In this work, the continuous in situ removal of the byproduct water through the 4 Å wide pores in an LINDE Type A (LTA) (grown on an α-Al2O3support) membrane reactor further increased the selectivity toward the economically desired product dimethylamine by 50%. This experimental finding can be explained by the release of adsorbed water blocking the catalytic site. Water removal through the hydrophilic LTA zeolite membrane allows methanol to adsorb at the acidic catalyst sites, which in turn accelerates the methylation rate of monomethylamine to the desired product dimethylamine. Further methylation to trimethylamine as the thermodynamically most favored product is not possible in narrow-pore catalysts because of space restrictions, but it takes place in the 12-membered-ring H-Mordenite (H-MOR) catalyst.