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5-(hydroxymethyl)furfural (HMF) is a key biomass derived platform chemicals used to produce fuel precursors or additives and value-added chemicals, synthesised by the cascade isomerisation of glucose and subsequent dehydration of reactively formed fructose to HMF over Lewis and Bronsted acid catalysts respectively. Zirconia is a promising catalyst for such reactions; however, the impact of acid properties of different zirconia phases is poorly understood. In this work, we unravel the role of the zirconia crystalline phase in glucose isomerisation and fructose dehydration to HMF. The Lewis acidic monoclinic phase of zirconia is revealed to preferentially facilitate glucose isomerisation, while the nanoparticulate tetragonal phase possesses Brønsted acid sites which favour fructose dehydration. Synergy between both zirconia phases facilitates cascade HMF production, with both catalysts investigated as physical mixtures in batch and flow reactor configurations. Using a physical mixture of only 15 wt% m-ZrO2 with 85 wt% t-ZrO2 in either batch or packed bed reactor configuration is sufficient to reach equilibrium conversion of glucose for subsequent dehydration by the t-ZrO2 component. Under continuous flow, a six-fold increase in HMF production was obtained when operating with a physical mixture of m- and t-ZrO2 compared to that from a single bed of t-ZrO2., (© 2024 Wiley‐VCH GmbH.)

Chemical activated carbons (PET-H 2 SO 4 and PET-KOH) were prepared from post-consumer polyethylene terephthalate (PET) wastes using pyrolysis under moderate reaction temperatures by changing pyrolysis time and chemical activating agents. The produced carbons were characterized and tested in adsorption reactions of manganese, chromium, and cobalt ions in aqueous solutions. Results showed a high percentage removal of these inorganic ions from water: 98 % for Mn 2+ , 87 % for Cr 3+ , and 88 % for Co 2+ . Freundlich isotherms gave a better fit to the experimental data obtained with good correlation coefficient values in the range of 0.99-1 compared to other isotherms. The pseudo-second order kinetic model best described the chemical adsorption process as an exchange of electrons between the carbon and inorganic ions in solutions. The diffusion models showed that the process is controlled by a multi-kinetic stage adsorption process. In summary, this work demonstrates that the production of activated carbon from PET waste bottles is a potential alternative to commercial activated carbon and can be considered a sustainable waste management technology for removing these non-biodegradable plastic wastes from the environment., (© 2023 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

Perovskite and spinel oxides are promising alternatives to noble metal-based electrocatalysts for oxygen evolution reaction (OER). Herein, a novel perovskite/spinel nanocomposite comprised of SrCo 0.4 Fe 0.6 O 3 and CoFe 2 O 4 (SCF/CF) is prepared through a simple one-step method that incorporates iron doping into a SrCoO 3- δ matrix, circumventing complex fabrication processes typical of these materials. At a Fe dopant content of 60%, the CoFe 2 O 4 spinel phase is directly precipitated from the parent SrCo 0.4 Fe 0.6 O 3 perovskite phase and the number of active B-site metals (Co/Fe) in the parent SCF can be maximized. This nanocomposite exhibits a remarkable OER activity in alkaline media with a small overpotentional of 294 mV at 10 mA cm -2 . According to surface states analysis, the parent SCF perovskite remains in its pristine form under alkaline OER conditions, serving as a stable substrate, while the second spinel CF is covered by 5/8 monolayer (ML) O*, exhibiting considerable affinity toward the oxygen species involved in the OER. Analysis based on advanced OER microkinetic volcano model indicates that a 5/8 ML O* covered-CF is the origin for the remarkable activity of this nanocomposite. The results reported here significantly advance knowledge in OER and can boost application, scale-up and commercialisation of electrocatalytic technologies toward clean energy devices., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

Photoreforming of lignocellulose biomass is widely recognised as a challenging but key technology for producing value-added chemicals and renewable hydrogen (H 2 ). In this study, H 2 production from photoreforming of organosolv lignin in a neutral aqueous solution was studied over a 0.1 wt % Pt/TiO 2 (P25) catalyst with ultraviolet A (UVA) light. The H 2 production from the system employing the lignin (~4.8 μmol g cat -1  h -1 ) was comparable to that using hydroxylated/methoxylated aromatic model compounds (i. e., guaiacol and phenol, 4.8-6.6 μmol g cat -1  h -1 ), being significantly lower than that from photoreforming of cellulose (~62.8 μmol g cat -1  h -1 ). Photoreforming of phenol and reaction intermediates catechol, hydroquinone and benzoquinone were studied to probe the mechanism of phenol oxidation under anaerobic photoreforming conditions with strong adsorption and electron transfer reactions lowering H 2 production from the intermediates relative to that from phenol. The issues associated with catalyst poisoning and low photoreforming activity of lignins demonstrated in this paper have been mitigated by implementing a process by which the catalyst was cycled through anaerobic and aerobic conditions. This strategy enabled the periodic regeneration of the photocatalyst resulting in a threefold enhancement in H 2 production from the photoreforming of lignin., (© 2023 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

CO 2 utilization is an important process in the chemical industry with great environmental power. In this work we show how CO 2 and H 2 can be reacted to form methanol on an iron(II) center and highlight the bottlenecks for the reaction and what structural features of the catalyst are essential for efficient turnover. The calculations predict the reactions to proceed through three successive reaction cycles that start with heterolytic cleavage of H 2 followed by sequential hydride and proton transfer processes. The H 2 splitting process is an endergonic process and hence high pressures will be needed to overcome this step and trigger the hydrogenation reaction. Moreover, H 2 cleavage into a hydride and proton requires a metal to bind hydride and a nearby source to bind the proton, such as an amide or pyrazolyl group, which the scorpionate ligand used here facilitates. As such the computations highlight the non-innocence of the ligand scaffold through proton shuttle from H 2 to substrate as an important step in the reaction mechanism., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The manipulation of carbon nitride (CN) structures is one main avenue to enhance the activity of CN-based photocatalysts. Increasing the efficiency of photocatalytic heterogeneous materials is a critical step toward the realistic implementation of sustainable schemes for organic synthesis. However, limited knowledge of the structure/activity relationship in relation to subtle structural variations prevents a fully rational design of new photocatalytic materials, limiting practical applications. Here, the CN structure is engineered by means of a microwave treatment, and the structure of the material is shaped around its suitable functionality for Ni dual photocatalysis, with a resulting boosting of the reaction efficiency toward many CX (X = N, S, O) couplings. The combination of advanced characterization techniques and first-principle simulations reveals that this enhanced reactivity is due to the formation of carbon vacancies that evolve into triazole and imine N species able to suitably bind Ni complexes and harness highly efficient dual catalysis. The cost-effective microwave treatment proposed here appears as a versatile and sustainable approach to the design of CN-based photocatalysts for a wide range of industrially relevant organic synthetic reactions., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

ZSM-5 zeolite nanoboxes with accessible meso-micro-pore architecture and strong acid sites are important in relevant heterogeneous catalysis suffering from mass transfer limitations and weak acidities. Rational design of parent zeolites with concentrated and non-protective coordination of Al species can facilitate post-synthetic treatment to produce mesoporous ZSM-5 nanoboxes. In this work, a simple and effective method was developed to convert parent MFI zeolites with tetrahedral extra-framework Al into Al-enriched mesoporous ZSM-5 nanoboxes with low silicon-to-aluminium ratios of ≈16. The parent MFI zeolite was prepared by rapid ageing of the zeolite sol gel synthesis mixture. The accessibility to the meso-micro-porous intra-crystalline network was probed systematically by comparative pulsed field gradient nuclear magnetic resonance diffusion measurements, which, together with the strong acidity of nanoboxes, provided superb catalytic activity and longevity in hydrocarbon cracking for propylene production., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Water electrolysis is one of the most promising methods to produce H 2 and O 2 as high potential fuels. Comparing the two half-reactions, the oxygen evolution reaction (OER) is the more difficult to be optimized and still relies on expensive noble metal-based catalysts such as Ru or Ir. In this paper, we prepared nanoparticles of HfN and Hf 2 ON 2 and tested them for the OER for the first time. The HfN sample, in particular, showed the highest activity, requiring an overpotential of only 358 mV at 10 mA cm -2 in Fe-free electrolyte and, above all, exhibiting long-term stability. This result places this system amongst one of the most promising catalysts for OER tested to date, in terms of sustainability, activity and stability. The prepared nanoparticles are small (less than 15 nm in diameter), well-defined in shape and crystalline, and were characterised before and after electrochemical testing also via electron microscopy (EM), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS)., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate-adsorbent interactions in liquid-saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T1/T2) is related to an adsorbate-adsorbent interaction energy, and we introduce a quantitative metric esurf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO2 anatase, TiO2 rutile, γ-Al2O3, SiO2, θ-Al2O3 and ZrO2) and show that esurf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the esurf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T1/T2 measurements may become a useful addition to the methods available to characterise liquid-phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate-surface interactions in liquid-phase catalysis., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The effect of ceria and zirconia grafting onto alumina (α and θ-δ phases) as supports for silicotungstic acid for the dehydration of glycerol to acrolein was studied. 30 % Silicotungstic acid (STA) supported on 5 % zirconia/δ,θ-alumina was the best catalyst, producing 85 % selectivity to acrolein at 100 % glycerol conversion, and it showed stable activity without using oxygen as a co-feed. The catalyst produced a STA of 90 g(acrolein)  kg(cat)(-1)  h(-1), which was greater than the STA simply supported on δ,θ-alumina, which only demonstrated 75 % selectivity towards acrolein. The effect of grafting on the support material was investigated by means of nitrogen adsorption, ammonia temperature-programmed desorption, thermogravimetric analysis, Raman spectroscopy, and powder X-ray diffraction. A pulsed-field gradient (PFG) NMR technique was also used to study diffusion processes associated with the catalysts. Diffusion studies of the grafted catalysts showed that zirconia contributes to the formation of more tortuous pathways within the pore structure, leading to the diminution of acid strength and making the catalyst less susceptible to coke formation., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In recent work, it was reported that changes in solvent composition, precisely the addition of water, significantly inhibits the catalytic activity of Au/TiO2 catalyst in the aerobic oxidation of 1,4-butanediol in methanol due to changes in diffusion and adsorption properties of the reactant. In order to understand whether the inhibition mechanism of water on diol oxidation in methanol is generally valid, the solvent effect on the aerobic catalytic oxidation of 1,3-propanediol and its two methyl-substituted homologues, 2-methyl-1,3-propanediol and 2,2-dimethyl-1,3-propanediol, over a Au/TiO2 catalyst has been studied here using conventional catalytic reaction monitoring in combination with pulsed-field gradient nuclear magnetic resonance (PFG-NMR) diffusion and NMR relaxation time measurements. Diol conversion is significantly lower when water is present in the initial diol/methanol mixture. A reactivity trend within the group of diols was also observed. Combined NMR diffusion and relaxation time measurements suggest that molecular diffusion and, in particular, the relative strength of diol adsorption, are important factors in determining the conversion. These results highlight NMR diffusion and relaxation techniques as novel, non-invasive characterisation tools for catalytic materials, which complement conventional reaction data., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The effect of water on the catalytic oxidation of 1,4-butanediol in methanol over Au/TiO(2) has been investigated by catalytic reaction studies and NMR diffusion and relaxation studies. The addition of water to the dry catalytic system led to a decrease of both conversion and selectivity towards dimethyl succinate. Pulsed-field gradient (PFG)-NMR spectroscopy was used to assess the effect of water addition on the effective self-diffusivity of the reactant within the catalyst. NMR relaxation studies were also carried out to probe the strength of surface interaction of the reactant in the absence and presence of water. PFG-NMR studies revealed that the addition of water to the initial system, although increasing the dilution of the system, leads to a significant decrease of effective diffusion rate of the reactant within the catalyst. From T(1) and T(2) relaxation measurements it was possible to infer the strength of surface interaction of the reactant with the catalyst surface. The addition of water was found to inhibit the adsorption of the reactant over the catalyst surface, with the T(1)/T(2) ratio of 1,4-butanediol decreasing significantly when water was added. The results overall suggest that both the decrease of diffusion rate and adsorption strength of the reactant within the catalyst, due to water addition, limits the access of reactant molecules to the catalytic sites, which results in a decrease of reaction rate and conversion., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)