A novel series membranes based on non-linear all-aromatic polyimides (PIs) was investigated with the aim to understand how the PI backbone geometry and local electrostatics govern gas transport and the ability to separate CO₂/CH₄ mixtures. Non-linear 3-ring aromatic diamines, with exocyclic bond angles varying between 120 and 134°, enable the design of high Tg (>276 °C) PIs. A polar 1,3,4-oxadiazole diamine (ODD) (μ = 3D) monomer and a non-polar m-terphenyl diamine (TPD) reference monomer were synthesized and coupled with 3 dianhydrides, i.e. ODPA, ODDA, and 6FDA. In 6FDA-based membranes CO₂ permeabilities (P_CO2) are the highest of the series. The 6FDA-ODD membrane shows excellent membrane performance with high P_CO2 values at all feed pressures. Up to 12 bar (6 bar CO₂) none of the membranes reached their plasticization pressure. The non-linear backbone geometry promotes CO₂ permeability, whereas the presence of an electrostatic dipole moment associated with the 1,3,4-oxadiazole heterocycle governs CO₂/CH₄ separation selectivity.

A novel electrochemical glucose sensor was developed, based on a multiwall carbon nanotubes (MWCNTs)-copper-1,3,5-benzenetricarboxylic acid (CuBTC)-epoxy composite electrode, named MWCNT-CuBTC. The electrode nanocomposite was prepared by a two-roll mill procedure and characterized morphostructurally by scanning electron microscopy (SEM). The CuBTC formed defined crystals with a wide size distribution, which were well dispersed and embedded in the MWCNTs. Its electrical conductivity was determined by four-point probe contact (DC) conductivity measurements. The electroactive surface area, determined using cyclic voltammetry (CV), was found to be 6.9 times higher than the geometrical one. The results of the electrochemical measurements using CV, linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), chronoamperometry (CA) and multiple pulse amperometry (MPA) showed that the MWCNT-CuBTC composite electrode displayed high electrocatalytic activity toward the oxidation of glucose and, as a consequence, very high sensitivity. The best sensitivity of 14,949 µAmM⁻¹cm⁻¹ was reached using MPA at the potential value of 0.6 V/SCE, which was much higher in comparison with other copper-based electrodes reported in the literature. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of an effective glucose sensor.

Cu-based metal-organic framework (MOF) microdevices are applied in sampling and preconcentration of nerve agents (NAs) diluted in gaseous streams. An in situ electrochemical-assisted synthesis of a Cu-benzene-1,3,5-tricarboxylate (BTC) thick film is carried out to functionalize a Cu-modified glass substrate. This simple, rapid, reproducible, and easy-to-integrate MOF synthesis approach enables the microfabrication of functional micro-preconcentrators with a large Brunauer-Emmett-Teller (BET) surface area (above 2000 cm2) and an active pore volume (above 90 nL) for the efficient adsorption of nerve agent molecules along the microfluidic channel 2.5 cm in length. The equilibrium adsorption capacity of the bulk material has been characterized through thermogravimetric analysis after exposure to controlled atmospheres of a sarin gas surrogate, dimethyl methylphosphonate (DMMP), in both dry and humid conditions (30% RH at 293 K). Breakthrough tests at the ppm level (162 mg/m3) reveal equilibrium adsorption capacities up to 691 mg/g. The preconcentration performance of such μ-devices when dealing with highly diluted surrogate atmosphere, i.e., 520 ppbV (2.6 mg/m3) at 298 K, leads to preconcentration coefficients up to 171 for sample volume up to 600 STP cm3. We demonstrate the potentialities of Cu-BTC micro-preconcentrators as smart first responder tools for "on-field" detection of nerve agents in the gas phase at relevant conditions.

High performance and commercially attractive mixed-matrix membranes were developed for H₂/CO₂ separation via a scalable hollow fiber spinning process. Thin (~300 nm) and defect-free selective layers were successfully created with a uniform distribution of the nanosized (~60 nm) zeolitic-imidazole framework (ZIF-8) filler within the polymer (polybenzimidazole, PBI) matrix. These membranes were able to operate at high temperature (150 °C) and pressure (up to 30 bar) process conditions required in treatment of pre-combustion and syngas process gas streams. Compared with neat PBI hollow fibers, filler incorporation into the polymer matrix leads to a strong increase in H₂ permeance from 65 GPU to 107 GPU at 150 °C and 7 bar, while the ideal H₂/CO₂ selectivity remained constant at 18. For mixed gas permeation, there is competition between H₂ and CO₂ transport inside ZIF-8 structure. Adsorption of CO₂ in the nanocavities of the filler suppresses the transport of the faster permeating H₂ and consequently decreases the H₂ permeance with total feed pressure down to values equal to the pure PBI hollow fibers for the end pressure of 30 bar. Therefore, the improvement of fiber performance for gas separation with filler addition is compromised at high operating feed pressures, which emphasizes the importance of membrane evaluation under relevant process conditions.

Coke deposition is one of the main challenges in the commercialisation of dry reforming of methane oversupported Ni catalysts. Besides the coke quantity, the structure of the deposits is also essential for thecatalyst lifetime. Accordingly, in this study, we analysed the effect of Na, K, and Cs promoters on boththese variables over Ni/ZrO2catalysts. Besides blocking the most active coke-forming sites already at lowloading, the promoting effect of the alkali metals is also contributed to by their coke gasification activity.To evaluate the additional impact of the latter, the behaviour of alkali-doped catalysts was compared tothat for Mn-doped catalysts, exclusively featuring the site-blocking promotion mechanism. While theconversion is barely affected by the type of promoter, it has a profound effect on the amount and thecomposition of carbon deposits formed during the reaction. Promoting with K or Mn reduces the cokecontent to a similar degree but with less carbon fibres observed in the case of K. The promotion by Cs andNa results in the lowest coke content. The superior performance of Cs and Na-doped Ni/ZrO2catalysts isattributed to the enhanced coke gasificationviacarbonate species on top of the site blocking effects.

Producing aromatics directly from the smallest hydrocarbon building block, methane, is attractive because it could help satisfy increasing demand for aromatics while filling the gap created by decreased production from naphtha crackers. The system that catalyzes the direct methane dehydroaromatization (MDA) best so far is Mo supported on zeolite. Mo has shown to outperform other transition metals (TMs). Here we attempt to explain the superiority of Mo by directly comparing Fe and Mo supported on HZSM-5 zeolite. To determine the most important parameters responsible for the superior performance of Mo, detailed characterization using X-ray absorption spectroscopy (XAS) techniques combined with catalytic testing and theoretical calculations are performed. The higher abundance of mono- A nd dimeric sites for the Mo system, their ease of carburization in methane, as well as intrinsically lower activation energy barriers of breaking the methane C-H bond over Mo explain the better catalytic performance. In addition, a pretreatment in CO is presented to more easily carburize Fe and thereby improve its catalytic performance.

Preparation methods are presented of thin dual layer membranes (DLM's) and mixed matrix membranes (MMM's) based on nanosheets of the Cu-BDC metal-organic framework (MOF, lateral size range 1–5 µm, thickness 15 nm) and commercially available poly(ethylene oxide)–poly(butylene terephthalate) (PEO–PBT) copolymer (Polyactive™) and their performances are compared in CO₂/N₂ separation. The MMMs and DLMs represent two extremes, on the one hand with well-mixed components and on the other hand completely segregated layers. Compared to the free-standing membranes, the thin PAN- and zirconia-alumina-supported MMMs showed significant enhancement in both permeance and selectivity. The support properties affect the obtained selective layer thickness and its resistance impacts the CO₂/N₂ selectivity. The permeance of thin DLM's is among the highest reported literature data of MOF based thin MMMs, but have a modest selectivity. Addition of the nanosheets in the thin MMMs improves the CO₂/N₂ selectivity of the already selective polymer further to 77. The nanosheets in the thin MMMs make a gutter layer on the PAN support superfluous. The small pore support ZrO₂-alumina does not need a gutter layer. XRD analysis reveals that the spatial distribution of MOF nanosheets and polymer chains packing were responsible for differences in the permeation performance of the free-standing, thin dual layer and mixed matrix membranes.

The active sites on the methane dehydroaromatization (MDA) catalyst Mo/HZSM-5 are very hard to characterize, because they are present in various geometries and sizes and only form under reaction conditions with methane at 700 °C. To address these issues an experimental strategy is presented that enables distinguishing different active sites for MDA present on Mo/HZSM-5 and helps determining the Mo charge, nuclearity and chemical composition. This approach combines a CO pretreatment to separate the active Mo site formation from coke formation, quasi-in situ spectroscopic observations using DNP, ¹³C NMR, CO IR and theory. This allows the discrimination between three different types of active sites. Distinct spectroscopic features were observed corresponding to two types of mono- or dimeric Mo (oxy-)carbide sites as well as a third site assigned to Mo₂C nanoparticles on the outer surface of the zeolite. Their formal Mo oxidation state was found to be between 4+ and 6+. Dynamic nuclear polarization (DNP) measurements of samples carburized in CO as well as in CH₄ confirm the assignment and also show that accumulated aromatic carbon covers the bigger Mo nanoparticles on the outer surface of the zeolite, causing deactivation. It was previously observed that after an initial period where no desired products are formed yet, benzene starts slowly forming until reaching its maximum productivity. Direct observation of the active site with ¹³C NMR confirmed that Mo-sites do not transform further once benzene starts forming, meaning that they are fully activated during the period where no desired products are observed yet. Therefore the slow increase of the benzene formation rate cannot be attributed to a further transformation of Mo sites.

We report the preparation and electrocatalytic performance of silver-containing gas diffusion electrodes (GDEs) derived from a silver coordination polymer (Ag-CP). Layer-by-layer growth of the Ag-CP onto porous supports was applied to control Ag loading. Subsequent electro-decomposition of the Ag-CP resulted in highly selective and efficient CO₂-to-CO GDEs in aqueous CO₂ electroreduction. Afterward, the metal-organic framework (MOF)-mediated approach was transferred to a gas-fed flow electrolyzer for high current density tests. The in situ formed GDE, with a low silver loading of 0.2 mg cm^-2, showed a peak performance of j_CO ≈ 385 mA cm^-2 at around -1.0 V vs RHE and stable operation with high FE_CO (>96%) at j_Total = 300 mA cm^-2 over a 4 h run. These results demonstrate that the MOF-mediated approach offers a facile route for manufacturing uniformly dispersed Ag catalysts for CO₂ electrochemical reduction by eliminating ill-defined deposition steps (drop-casting, etc.) while allowing control of the catalyst structure through self-assembly.

The mechanism of methane activation on Mo/HZSM-5 is poorly described, despite the great interest in methane dehyd roa romatization (MDA) to replace oil refineries for producing aromatics. It is difficult to assess the exact nature of the active site due to fast coking. By pre-carburizing Mo/HZSM-5 with carbon monoxide, the active site for MDA can be isolated and studied without the formation of coke. This strategy helped us examine how methane is activated on the catalytic site by carrying out MDA using isotopically labelled methane (^{1 3} C H ₄ ) . We show that carbon originating from the preformed carbide is incorporated into the main products of the reaction, ethylene and benzene, demonstrating the dynamic nature of these active sites.

The catalytic performance of the bifunctional catalyst Mo/HZSM-5 for methane dehydroaromatization (MDA) depends on the Mo dispersion and on zeolite acidity. Here we separately quantify the effect of dispersion and the effect of acidity on aromatic yields and coke selectivity. Also, the effect of porosity on the same is quantitatively assessed. For that, a suite of 17 samples with varying Mo dispersion were synthesized by means of several methods, including chemical vapor deposition with MoCl ₅ , MoO ₂ Cl ₂ and Mo(CO) ₆ as precursors and the conventional methods, incipient wetness impregnation and solid ion exchange. These catalysts were characterized with pyridine IR-spectroscopy, XPS, UV–vis spectroscopy, N ₂ adsorption, XRD, TGA and ²⁷ Al MAS NMR. The combined results yielded a measure of how much Mo is anchored to the zeolite as well-defined cationic species and how much is present as bigger clusters on the outer surface of the zeolite. Through relating these characterization results to the catalytic behavior of the catalysts, it was found that the maximum instantaneous benzene and naphthalene yields as well as the integral selectivities during methane dehydroaromatization linearly increase with the amount of Mo present as mono- or dimeric species. At the same time, the selectivity to coke increases with the amount of Mo present as bigger clusters or nanoparticles on the outer surface of the zeolite. The number of Mo cationic sites is the most important factor determining the activity of Mo/HZSM-5 for low loadings of Mo. But at higher loadings, the high rate of aromatics formation requires an easily accessible pore structure as well.