MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy

The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium’s redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed

Synergic Effect of Isolated Ce3+ and Ptd+ Species in UiO-66(Ce) for Heterogeneous Catalysis

[EN] In this work, wehave synthesized through an efficient electrostaticdeposition a Pt single-atom catalyst (SAC) supported on a Ce-MOF.The basic solution employed in the impregnation process favors thedeprotonation of the hydroxyl groups allocated on the clusters thatcan easily interact with the cationic Pt species. The resulting material,denoted as Pt/UiO-66(Ce), shows an increment of Ce3+ content,as demonstrated by UV-vis and Ce L-3-edge XANES spectroscopy.These Ce3+ species and their corresponding oxygen vacanciesare able to accommodate very disperse Pt single sites. Moreover, PtL3-edge XANES and CO-FTIR spectroscopy confirm the cationicnature of the supported Pt & delta;+ (2+ < & delta; <4+). For comparison purpose, we have synthesized and characterizeda well-known Pt single-site catalyst supported on nanocrystallineceria, denoted as Pt/nCeO(2). Since thesimultaneous presence of Ce3+ and Pt & delta;+ on the MOF clusters were able to activate the oxygen molecules andthe CO molecule, respectively, we tested Pt/UiO-66(Ce) for the COoxidation reaction. Interestingly, this catalyst showed & SIM;six-foldincrement in activity in comparison with the traditional Pt/nCeO(2) material. Finally, the characterizationafter catalysis reveals that the Pt nature is preserved and that theactivity is maintained during 14 h at 100 & DEG;C without any evidenceof deactivation.S.R.-B. acknowledges the Margarita Salas grant financed by the Ministerio de Universidades, Spain, and also funded by the European Union-Next Generation EU. S.R.-B. and S.B. acknowledge support from the Project CH4.0 under the MUR program ?Dipartimenti di Eccellenza 2023-2027? (CUP: D13C22003520001). B.B., A.C., and M.M. acknowledge the financial support of the Spanish Government through PID2021-122755OB-I00 funded by MCIN/AEI/10.13039/501100011033 and TED2021-130739B-I00 funded by MCIN/AEI/10.13039/501100011033/EU/PRTR), and of the Generalitat Valenciana through AICO/2021/201. B.B., A.C., and M.M. are also thankful for the Severo Ochoa financial support by the Spanish Ministry of Science and Innovation (CEX2021-001230-S/funding by MCIN/AEI/10.13039/501100011033).Rojas-Buzo, S.; Bohigues-Vallet, B.; Salusso, D.; Corma Canós, A.; Moliner Marin, M.; Bordiga, S. (2023). Synergic Effect of Isolated Ce3+ and Ptd+ Species in UiO-66(Ce) for Heterogeneous Catalysis. ACS Catalysis. 13(13):9171-9180. https://doi.org/10.1021/acscatal.3c0050291719180131

Zn Redistribution and Volatility in ZnZrOx Catalysts for CO2 Hydrogenation

ZnO–ZrO2 mixed oxide (ZnZrOx) catalysts are widely studied as selective catalysts for CO2 hydrogenation into methanol at high-temperature conditions (300–350 °C) that are preferred for the subsequent in situ zeolite-catalyzed conversion of methanol into hydrocarbons in a tandem process. Zn, a key ingredient of these mixed oxide catalysts, is known to volatilize from ZnO under high-temperature conditions, but little is known about Zn mobility and volatility in mixed oxides. Here, an array of ex situ and in situ characterization techniques (scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Infrared (IR)) was used to reveal that Zn2+ species are mobile between the solid solution phase with ZrO2 and segregated and/or embedded ZnO clusters. Upon reductive heat treatments, partially reversible ZnO cluster growth was observed above 250 °C and eventual Zn evaporation above 550 °C. Extensive Zn evaporation leads to catalyst deactivation and methanol selectivity decline in CO2 hydrogenation. These findings extend the fundamental knowledge of Zn-containing mixed oxide catalysts and are highly relevant for the CO2-to-hydrocarbon process optimization.publishedVersio

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Combining X-ray Diffraction and X-ray Absorption Spectroscopy to Unveil Zn Local Environment in Zn-Doped ZrO2 Catalysts

&lt;p&gt;K-space EXAFS spectra; additional PXRD results; EXAFS fitting for reference t-ZrO2; fwhm analysis of first derivative of the Zr K-edge XANES main edge; EXAFS fitting for reference h-ZnO; test Zr K-edge EXAFS fitting of ZrZn-5 using a c-ZrO2 model; additional details on input structures employed in Zn K-edge EXAFS fitting; additional details on cluster size evaluation; additional details on &lt;i&gt;in situ&lt;/i&gt; XAS data during activation in H2 and related EXAFS analysis using the Einstein model; &lt;i&gt;in situ&lt;/i&gt; XAS data under reaction conditions (CO2/H2, 300 °C, 15 bar)&nbsp;&lt;/p&gt