Quantifying adsorption thermodynamics on heterogeneous catalysts remains challenging because macroscopic techniques yield averaged parameters, while vibrational spectra often contain strongly overlapping contributions from multiple adsorbed species. Here we introduce an infrared (IR)-chemometric framework that extracts site-specific adsorption thermodynamics directly from experimental IR isotherms and we benchmark it against independent microcalorimetry and density functional theory (DFT) calculations. Difference IR spectra recorded for isobutanol adsorption on H-ZSM-5 (MFI) were analysed by principal component analysis and multivariate curve resolution (MCR-ALS) under soft constraints (monotonic concentration profiles, spectral normalisation), and further refined using a hard-soft strategy in which concentration profiles are constrained by an adsorption model. The analysis reveals three adsorption modes associated with bridging Br & oslash;nsted OH groups, extra-framework Al-OH species, and silanols, providing representative pure-component spectra and site-resolved adsorption isotherms. The thermodynamic trends and site hierarchy obtained from IR-MCR-ALS are consistent with independent microcalorimetry measurements and density functional theory calculations, validating the approach. More broadly, IR-MCR-ALS offers a transferable route to quantitative, site-resolved adsorption thermodynamics in complex catalysts.

Keggin heteropolyacids (HPAs) are powerful catalytic materials because of their particularly high acid strength. Dispersing them on a support is a commonly adopted strategy to overcome their low specific surface area and increase their recoverability. In this regard, their dispersion needs to be characterized. In situ IR measurements upon pyridine adsorption (IR-py) has recently been carried out on TiO2-supported H3PW12O40 to assess its dispersion quantitatively for the first time. Herein, we report the precautions to take when extending this approach to another Keggin HPA, namely H3PMo12O40 (HPMo). In particular, the purpose of the current work is to comment on the earlier published work rather to present a full study and to show that, for reducible HPAs like H3PMo12O40, reoxidation is required to employ IR-py as a tool to quantify dispersion. For these reasons, no catalytic tests are provided and the extent of reoxidation is not measured/characterized as well.

The selective dehydration of isobutanol to linear butenes catalyzed by acidic ferrierite (H-FER) has been investigated by operando IR spectroscopy under close batch conditions and along a temperature ramp. The employed apparatus permits to alternatively acquire spectra of both the gas phase composition and the species adsorbed on the H-FER surface, thus providing fundamental insights onto the products formation and the reaction intermediates formed on the catalyst surface. In the gas phase, the high selectivity for linear butenes was confirmed in the first phases of the reaction, followed by a slower isomerization to isobutene and by the formation of heavier compounds due to secondary processes. Detailed MCR-ALS analysis of the adsorbed species’ spectra permitted to also identify and quantify adsorbed 2-butanol and trans-2-butene on the H-FER surface, providing a first indication of the alcohol isomerization as a key step in the reaction mechanism. The proposed mechanism was evaluated by microkinetic modelling of both gas phase and surface concentration profiles, showing that the consecutive isomerization of isobutanol to adsorbed 2-butanol followed by its dehydration to trans-2-butene is more favorable than the one-step dehydration-isomerization of isobutanol. In contrast, the direct dehydration of isobutanol to isobutene was found to be slower over the entire investigated temperature range.

The selective removal of oxygenates like phenol is a key challenge in upgrading biofuels. This study evaluates the adsorption performance and selectivity of zeolites (HY2.9, USY22, and USY40) and oxides (Al2O3, SBA-15) for phenol in the presence of fuel representative co-molecules (toluene, cyclohexane, and 2,3-dimethyl-2-butene) using batch experiments and, notably, operando ATR-IR spectroscopy. Batch adsorption capacities followed the order SBA-15 > HY2.9 > USY40 approximate to USY22 > Al2O3. Performance depends on a combination of factors such as specific surface area, pore size and pore density, as well as the density and nature of the acid sites. While cyclohexane had negligible impact, toluene and dimethylbutene induced competitive adsorption or site poisoning, with effects being nearly cumulative in complex mixtures. ATR-IR measurements not only corroborated batch trends but also provided molecular-level insights, demonstrating its relevance as a rapid, operando screening tool to assess adsorption mechanisms, selectivity, and regeneration potential with minimal material consumption. The findings highlight the advantage of weakly acidic or non-acidic adsorbents in complex mixtures and underscore the utility of ATR-IR for efficient adsorbent evaluation.

Accurate assessment of the metal dispersion is known to be important in the field of catalysis as these data are used to calculate the turnover frequency of a given reaction on a given metal. This study shows that N2 can be used as a Fourier transform infrared spectroscopy (FTIR) probe molecule not only qualitatively but also quantitatively. For the first time, it is found that the integrated molar absorption coefficient of N2 adsorbed on the hydroxyapatite (HAp) supports (epsilon N2-HAp = 0.092 +/- 0.008 cm/mu mol) does not depend on the chemical composition of HAp, while that of N2 adsorbed on the HAp-supported Ru0 nanoparticles of about 2.2 nm (epsilon N2-Ru 0: 0.5-1.03 cm/mu mol) is sensitive to the chemical composition of HAp. This study also shows, for the first time, that epsilon N2-Ru 0 increases with increasing electron density of the Ru0 nanoparticles, as monitored by the position of the maximum of the absorption band of the N2 stretching vibration at about 2200 cm-1 (nu N2-Ru 0), with a remarkable correlation between epsilon N2-Ru 0 and nu N2-Ru 0. The epsilon N2-Ru 0 values are 2 orders of magnitude smaller than the previously reported integrated molar absorption coefficients of CO (epsilon CO-Ru 0). Finally, epsilon N2-HAp and epsilon N2-Ru 0 allow us to estimate the Ru dispersion, which is in remarkable agreement with that determined by transmission electron microscopy (TEM).

The renewed interest in supported MoS2 for use in the water-gas shift (WGS) reaction is due to its tolerance towards sulfur impurities present in syngas derived from biomass. The exposure of different amounts of M-and Sactive edge sites defines the morphology of the sulfide-phase, which can be revealed indirectly by IRspectroscopy during CO adsorption (IR/CO) or directly using transmission electron-microscopy in scanning mode with high angular annular dark field imaging. Both the WGS activity and the implied mechanisms are linked to the MoS2-morphology. On TiO2, the sulfide slabs have exposed M-edge sites only associated with a triangular shape, while on SiO2 a higher S/M-edge ratio is observed which is ascribed to a more hexagonal shape. The WGS activity of these catalysts is marked by a strong initial deactivation. Characterization of the catalysts by IR/CO after contact with the reactant flow at reaction temperature permits the identification of M-edge sites to undergo S/O exchange under H2O flow, whereas S-edge sites do not. Interestingly, these O-exchanged M-edge sites are stable under subsequent CO flow when supported on SiO2, but are partially recovered when supported on TiO2 simultaneously with support sites. These different findings lead us to propose different reaction mechanisms, confirmed by operando tests, revealing the sole occurrence of a COS-redox pathway on MoS2/SiO2, and of the associative mechanism through the reaction of CO with hydroxyl groups on MoS2/TiO2. The addition of H2S in the reactant flow allows to limit the deactivation process and to reach a steady state.

Nitrogen oxides represent one of the main threats for the environment. Despite decades of intensive research efforts, a sustainable solution for NOx removal under environmental conditions is still undefined. Using theoretical modelling, material design, state-of-the-art investigation methods and mimicking enzymes, it is found that selected porous hybrid iron(II/III) based MOF material are able to decompose NOx, at room temperature, in the presence of water and oxygen, into N2 and O2 and without reducing agents. This paves the way to the development of new highly sustainable heterogeneous catalysts to improve air quality.

Herein we report on a robust microporous aluminum tetracarboxylate framework, MIL-120(Al)-AP, (MIL, AP: Institute Lavoisier and Ambient Pressure synthesis, respectively), which exhibits high CO2 uptake (1.9 mmol g-1 at 0.1 bar, 298 K). In situ Synchrotron X-ray diffraction measurements together with Monte Carlo simulations reveal that this structure offers a favorable CO2 capture configuration with the pores being decorated with a high density of µ2-OH groups and accessible aromatic rings. Meanwhile, based on calculations and experimental evidences, moderate host-guest interactions Qst (CO2) value of MIL-120(Al)-AP (~40 kJ mol-1) is deduced, suggesting a relatively low energy penalty for full regeneration. Moreover, an environmentally friendly ambient pressure green route, relying on inexpensive raw materials, is developed to prepare MIL-120(Al)-AP at the kilogram scale with a high yield while the MOF is further shaped with inorganic binders as millimeter-sized mechanically stable beads. First evidences of its efficient CO2/N2 separation ability are validated by breakthrough experiments while IR operando experiments indicate a kinetically favorable CO2 adsorption over water. Finally, a techno-economic analysis gives an estimated production cost of about 13 $/kg, significantly lower than for other benchmark MOFs. These advancements make MIL-120(Al)-AP an excellent candidate as an adsorbent for industrial scale CO2 capture processes.

The one-step catalytic conversion of bio-based ethanol to 1,3-butadiene is an attractive way to produce this important C4 building block, to be exploited as a sustainable drop-in chemical in the tire and nylon industry. For this catalytic process, bifunctional catalysts combining both redox and acidic properties are required. Here, we leverage non-hydrolytic sol-gel (NHSG) chemistry to prepare tailored Cu-Ta-SiO2 catalysts featuring an open texture, dispersed acidic Ta sites, and small Cu nanoparticles. In the ether route, silicon tetrachloride and tantalum pentachloride undergo polycondensation reactions with diisopropyl ether as the oxygen donor. In the acetamide elimination route, silicon tetraacetate reacts with pentakis(dimethylamido)tantalum(V). In both routes, copper(II) acetylacetonate is added and trapped in a tantalosilicate matrix. Upon calcination, CuO nanoparticles form and the resulting bifunctional material develop a mesoporous texture with specific surface areas in the 650-950 m(2) g(-1) range, pore volumes between 0.75 and 0.90 cm(3) g(-1), and average pore diameters above 3 nm. With the help of NH3-TPD, FTIR, CO- and pyridine-adsorbed FTIR, XRD, XPS, and STEM-EDS, we demonstrate that the catalysts made via the acetamide elimination route show higher performance in the ethanol-to-butadiene reaction, with low selectivity in dehydration byproducts, owing to moderate Lewis acidity, smaller Cu nanoparticles, and higher active site proximity. After optimization of the Ta and Cu loadings, a butadiene productivity as high as 0.38 g(BD) g(cat)(-1) h(-1) is obtained, surpassing state-of-the-art catalysts with similar formulations and tested under similar reaction conditions.

We report the development of a new method of investigation of the mass transport properties of acidic zeolite-based materials aiming to overcome the limitations of classical approaches. It consists in hyphenating gravimetric analysis and infrared spectroscopy. The former allows assessing the diffusion from the gas phase to all the porosity, while IR allows for selective assessment of diffusion to the zeolite active sites located in the micropores. Furthermore, the data are processed by an original methodology allowing the recovery of the distribution of diffusion domains by inversion of the integral equations describing the uptake curves or the evolution of the infrared spectra. The combination of gravimetric analysis and IR spectroscopy makes it possible to monitor and distinguish diffusion within the various components of the material. The methodology has been applied to the isooctane uptake in the mechanical mixture of FAU and MFI zeolites. Analysis of both gravimetric uptake curves and evolving infrared spectra allows distinguishing and assigning diffusion domains to the H-FAU and H-MFI components of the mixture, with high and low effective diffusion rate constants, respectively. The advantages and limits of the methodology are discussed.

Here, we report a new approach for preparing zeolite-polymer core-shell-like materials with hierarchical porosity via photopolymerization of trifunctional acrylic monomer (TMPTA) under UV-visible irradiation using a bifunctional Silane-based Photoinitiator (SPI-1) as coupling agent. The free radicals generated on the surface of zeolites initiate the polymerization of the diluted monomers, creating an external and mesoporous polymer shell layer. The efficiency of the photopolymerization process and the textural properties of synthesized materials are investigated using different techniques, including PXRD, TGA, UV-Vis, FTIR, SEM, and TEM. The accessibility to the pores of the zeolite core is investigated by N2 physisorption at 77 K and other probe molecules using IR spectroscopy. Interestingly, the results demonstrate a good covering of the zeolite surfaces by polymers shell. The new approach is highly repetitive and reproducible, and the accessibility to the zeolite's micropores is preserved at around 90%, which is not reported previously. The hybrid materials show higher hydrophobicity and higher ethanol adsorption capacities compared to the parent material and are potential candidates for ethanol dehydration, demonstrating a new and easy way for preparing zeolite/polymer hybrid materials for various applications such as ethanol dehydration.

Advanced IR vibrational spectroscopic techniques, e.g., using a coupled gravimetric-IR surface analyzer (AGIR) and a high-throughput in situ IR cell (Carroucell), have been used for the quantitative studies of the adsorption and coadsorption of ethanol and water on MFI zeolites with different Si/Al ratios. The AGIR coupling is a powerful tool for the accurate determination of the molar adsorption coefficients during coadsorption experiments since their evaluation is based on the measurement of the exact amount of adsorbed species. The use of the Carroucell set up allows characterizing all the samples simultaneously, strictly in the same gaseous and temperature environment. The molar absorption coefficients of pure adsorbed ethanol and water are determined: their values are constant whatever the Si/Al ratio of the MFI zeolites. Moreover, these coefficients are found to be identical in the case of the water-ethanol coadsorption experiments. Their use allows obtaining the exact quantity of each adsorbate specie in the binary system. At low partial pressures, the unary water adsorption experiments suggest that the amount of adsorbed water results mainly from the preferential adsorption on Brønsted acid sites in tetrameric clusters. In contrast, the adsorption of EtOH occurs on both silanol groups and Brønsted acid sites (BASs). The effect of the Si/Al ratio is only observed at relatively low partial pressures. The effect of the Si/Al ratio on the ethanol adsorption capacity is also investigated. This study directs the choice of an appropriate zeolite once it is used in membranes for drying ethanol.

AbstractEncapsulating ultrasmall Cu nanoparticles inside Zr‐MOFs to form core–shell architecture is very challenging but of interest for CO2reduction. We report for the first time the incorporation of ultrasmall Cu NCs into a series of benchmark Zr‐MOFs, without Cu NCs aggregation, via a scalable room temperature fabrication approach. The Cu NCs@MOFs core–shell composites show much enhanced reactivity in comparison to the Cu NCs confined in the pore of MOFs, regardless of their very similar intrinsic properties at the atomic level. Moreover, introducing polar groups on the MOF structure can further improve both the catalytic reactivity and selectivity. Mechanistic investigation reveals that the CuIsites located at the interface between Cu NCs and support serve as the active sites and efficiently catalyze CO2photoreduction. This synergetic effect may pave the way for the design of low‐cost and efficient catalysts for CO2photoreduction into high‐value chemical feedstock.

Here, we report the use of new bifunctional silane-based type-1 photoinitiator (SPI-1) as a coupling agent for photopolymer filler and silica grafting. The SPI-1 is grafted on the surface of silica nanoparticles via interactions between the ethoxy group of the silane and the silanol groups of the silica surface. The grafted particles are then dispersed or embedded in/with acrylate polymer by a direct photopolymerization process. The materials were characterized using different techniques including UV-vis spectroscopy, FTIR, TGA, and TEM. Their mechanical properties and the surface morphology were also investigated using AFM and DMA analyses. A significant change and enhancement of the mechanical properties of the newly synthesized materials were observed with respect to that of the unmodified silica. The analysis of the morphology at the microscale level reveals interesting information on the origin of this enhancement and on the dispersion of the filler in the polymer matrix.

Air pollution is an epochal concern, particularly in urban areas, and is linked to combustion processes 1 . The emission of nitrogen oxides (NOx) constitutes a critical environmental problem, and it can affect severely human health2,3,4 . At ambient temperature and pressure NOx decomposition is thermodynamically favoured; however, this process is kinetically inhibited, owing to a high activation energy5,6 . To date, no reported catalysts have had the required properties to lower the activation energy of this process without the help of coreacting agents and high temperatures7,8,9 . Here, we show that NO conversion to molecular nitrogen can be achieved at room temperature in the presence of O2 and H2O vapour, and in the absence of any further reducing agent, using iron-based Metal-Organic Frameworks (MOFs). Further, we demonstrate that MOFs work similarly to enzymes, but are stable in environments unfriendly to living matter. These findings open large perspectives on the solution of stringent problems in chemistry, such as the removal of pollutants or the activation of highly stable molecules.

Materials for the controlled release of nitric oxide (NO) are of interest for therapeutic applications. However, to date, many suffer from toxicity and stability issues, as well as poor performance. Herein, we propose a new NO adsorption/release mechanism through the formation of nitrites on the skeleton of a titanium-based metal-organic framework (MOF) that we named MIP-177, featuring a suitable set of properties for such an application: (i) high NO storage capacity (3 mu mol mg(solid)(-1)), (ii) excellent biocompatibility at therapeutic relevant concentrations (no cytotoxicity at 90 mu g mL(-1) for wound healing) due to its high stability in biological media (<9 % degradation in 72 hours) and (iii) slow NO release in biological media (approximate to 2 hours for 90 % release). The prospective application of MIP-177 is demonstrated through NO-driven control of mitochondrial respiration in cells and stimulation of cell migration, paving the way for the design of new NO delivery systems for wound healing therapy.