dagksan

• Skorynina, Alina A.; Lazzarini, Andrea; Sannes, Dag Kristian; Kozyr, Elizaveta G.; Ahoba-Sam, Christian & Bordiga, Silvia [Show all 8 contributors for this article] (2024). The structure of Pd-functionalized UiO-67 during CO2 hydrogenation. Journal of Materials Chemistry C. ISSN 2050-7526. 12(10), p. 3564–3572. doi: 10.1039/d3tc04175a. Full text in Research Archive
• Sannes, Dag Kristian; Pulumati, Sri Harsha; Skúlason, Egill; Flores, Ainara Nova & Olsbye, Unni (2024). CO<inf>2</inf> hydrogenation to methanol over Pt functionalized Hf-UiO-67 versus Zr-UiO-67. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 382(2282). doi: 10.1098/rsta.2023.0269. Full text in Research Archive Show summary

  Sustainable methanol formation from CO2/H2 is potentially a key process in the post-fossil chemical industry. In this study, Hf- and Zr-based metal-organic framework (MOF) materials with UiO-67 topology, functionalized with Pt nanoparticles, have been tested for CO2 hydrogenation at 30 bar and 170–240°C. The highest methanol formation rate, 14 molmethanol molPt−1 h−1, was obtained over a Hf-based catalyst, compared with the maximum of 6.2 molmethanol molPt−1 h−1 for the best Zr-based analogue. However, changing the node metal did not significantly affect product distribution or apparent activation energy for methanol formation (44–52 kJ mol−1), strongly indicating that the higher activity of the Hf-based analogues is associated with a higher number of active sites. Both catalysts showed stable catalytic performance during testing under kinetic conditions, but the addition of 2 vol% water to the feed induced catalyst deactivation, in particular the Hf-MOFs. Interestingly, mainly methanol and methane formation rates decreased, while CO formation rates were less affected by deactivation. No direct correlation was found between catalytic stability and framework stability (crystallinity, specific surface area). Experimental and computational studies suggest that water adsorption strength to the MOF node may affect the relative catalytic stability of Hf-UiO-67-Pt versus Zr-UiO-67-Pt methanol catalysts.

• Sannes, Dag Kristian; Øien-Ødegaard, Sigurd; Aunan, Erlend; Nova, Ainara & Olsbye, Unni (2023). Quantification of Linker Defects in UiO-Type Metal-Organic Frameworks. Chemistry of Materials. ISSN 0897-4756. 35(10), p. 3793–3800. doi: 10.1021/acs.chemmater.2c03744. Full text in Research Archive Show summary

  Metal–organic frameworks (MOFs) are nanoporous materials composed of organic linkers and inorganic nodes. The large variety of linkers and nodes and the multiple ways to combine them make MOFs highly tunable materials, which are thoroughly studied for their use in, e.g., catalysis, gas capture, and separation. The chemistry of MOFs is further enriched by defects, e.g., missing linker defects, which provide active sites for catalysis or anchoring sites for introducing new functionalities. A commonly reported method to quantify linker defects assumes the presence of one type of linker and the complete removal of capping agents, solvents, and other impurities upon activation at high temperature, e.g., 400 °C (M-400). However, attempts to use this method for MOFs containing different types of linkers, also called multivariate MOFs (MTV-MOFs), or capping agents that are not completely removed at 400 °C, give inaccurate results and hamper comparing results from different publications. In this work, we have developed a new procedure to compute missing linker defects in Zr-based MOFs using standard analytical techniques to quantify the capping agents that remain in the MOF upon activation at 200 °C (M-200). This method, which has been tested in UiO-66/67 based MOFs, should be applicable to any MOF that (1) has known decomposition products, (2) has no missing cluster defects, (3) has empty pores or contain species that can be quantified after activation, and (4) has a known node composition at 200 °C.

• Tezel, Elif; Sannes, Dag Kristian; Svelle, Stian; Szilagyi, Petra Agota & Olsbye, Unni (2023). Direct CO<inf>2</inf> to methanol reduction on Zr<inf>6</inf>-MOF based composite catalysts: a critical review. Materials Advances. doi: 10.1039/d3ma00345k. Full text in Research Archive Show summary

  The pressing problem of climate change on account of anthropogenic greenhouse-gas emissions underlines the necessity for carbon capture and utilisation technologies. Several heterogeneous catalyst systems allowing the conversion of waste CO2 into desirable products, such as methanol, have emerged as promising and potentially viable solutions to this perennial problem. In particular, composite catalysts based on hexanuclear zirconium metal–organic framework matrices have shown much promise in the direct conversion of CO2 into value-added and useful products. Herein, we critically review the literature in this area and relate differences in composition, defect chemistry, and structural characteristics, their reaction conditions with their performance and stability in the thermocatalytic hydrogenation of CO2 to methanol, on the basis of both experimental and theoretical studies. We also highlight the obstacles in directly comparing the performance of these systems for CO2 hydrogenation and suggest potential solutions and opportunities for further advancement.

• Pulumati, Sri Harsha; Sannes, Dag Kristian; Jabbour, Christia R.; Mandemaker, Laurens D. B.; Weckhuysen, Bert M. & Olsbye, Unni [Show all 8 contributors for this article] (2023). Mechanistic Insights in the Catalytic Hydrogenation of CO<inf>2</inf> over Pt Nanoparticles in UiO-67 Metal-Organic Frameworks. ACS Catalysis. 14(1), p. 382–394. doi: 10.1021/acscatal.3c03401. Full text in Research Archive Show summary

  Metal nanoparticles (NPs) encapsulated within Zr-based UiO-67 metal–organic frameworks (MOFs) have increased selectivity toward methanol in CO2 reduction reactions. However, the reduction mechanism in these systems remains unclear. We built upon prior work examining the synergistic interaction between Pt nanoparticles and Zr6O4(OH)4 clusters in UiO-67 and developed five distinct models representing the possible active sites in the Pt ⊂ MOF system. Density functional theory (DFT) calculations were employed to elucidate the CO2 reduction mechanism toward methanol, methane, and CO formation. Our findings support previous evidence showing that the interface between the Zr6O4(OH)4 cluster and platinum nanoparticles plays a crucial role in the activation of CO2 to CO or formate intermediates and its further reduction to methane and methanol, respectively. Furthermore, we found different CO2 hydrogenation mechanisms for interfaces involving Pt-flat terraces and Pt-edges. On Pt terraces and interfaces near Pt terraces, the reaction goes via CO, which can be desorbed as CO(g) or be further reduced to methane. On interfaces near Pt-edges, the reaction proceeds via formate and preferably forms methanol over methane. We designed experiments to validate our computational insights involving large and small Pt nanoparticles interacting with Zr6O4(OH)4 clusters. These experiments showed that only CO and methanol were formed when smaller nanoparticles were present. Notably, methane formed with CO and methanol in the presence of larger nanoparticles, highlighting the need for flat platinum surfaces at the interfaces for methane formation. We could also associate the IR signals corresponding to CO and bidentate formate with platinum nanoparticles and Zr6O4(OH)4 clusters, respectively. Theoretical models and experimental data provided us with insights into the complexity of the reaction mechanism and emphasized the significance of understanding both the individual components of the catalytic system and their interactions in enhancing catalytic activity.

View all works in NVA

• Sannes, Dag Kristian; Øien-Ødegaard, Sigurd; Aunan, Erlend; Flores, Ainara Nova & Olsbye, Unni (2023). Quantification of linker defects in UiO-type metal-organic frameworks. Full text in Research Archive
• Sannes, Dag Kristian; Øien-Ødegaard, Sigurd; Aunan, Erlend; Nova, Ainara & Olsbye, Unni (2022). Reliable determination of linker defects in UiO-type metal-organic frameworks. Full text in Research Archive
• Sannes, Dag Kristian; Øien-Ødegaard, Sigurd; Aunan, Erlend; Nova, Ainara & Olsbye, Unni (2022). Reliable determination of linker defects in UiO-type metal-organic frameworks. Full text in Research Archive
• Sannes, Dag Kristian & Lillerud, Karl Petter (2020). Synthesis and characterization of 2,6-NDC zirconium MOF. Universitetet i Oslo. Full text in Research Archive

View all works in NVA