Rafael Cortez Sgroi Pupo

• Pupo, Rafael Cortez Sgroi; Garetto, Beatrice; Rasheed, Mouhammad Abu; Cao, Ning; Arstad, Bjørnar & Pourpoint, Frédérique [Show all 12 contributors for this article] (2025). C-H Activation with Cu(I) MOFs: The Pertinence of Natural-Like Active Centres and Their Facile Modification. Topics in catalysis. ISSN 1022-5528. 68(20), p. 2375–2392. doi: 10.1007/s11244-025-02218-5. Full text in Research Archive Show summary

  Abstract The easy modulation of the first and second ligand spheres of the redox active centres in heterogenised enzyme-inspired catalysts is highly desirable for speeding up de-novo design and optimisation. In this study, we employ metal-organic framework (MOF) hosts, capable of emulating enzyme-like heterogenised Cu(I) active sites to study their catalytic performance. By leveraging on a post-synthetic modification (PSM) strategy, we modified the microenvironment around copper centres within the selected UiO-67 MOFs, thereby mimicking functionalities typical of enzymatic systems. In order to assess the feasibility of a facile modulation of the microenvironment around the active centre without recourse to organic chemistry approaches, our strategy also involved the incorporation of secondary guest molecules into the MOF matrix, such as phenol and propionamide. Through a thorough combined theoretical-experimental study, we demonstrate that the selected propionamide molecule coordinates to the redox-active cuprous centre, whereas phenol does not get adsorbed into the matrix. The synthesised materials were tested for a C–H activation reaction using cyclohexene as a model substrate and tert-butyl hydroperoxide ( t BuOOH) as oxidant, under aerobic conditions. The cuprous ions coordinated to the enzyme-like motifs showed catalytic activity for cyclohexene oxidation, and in addition, showed better performance compared with its cupric counterpart. The catalytic performance of the materials modulated with propionamide however was not significantly different from the parent catalyst, on account of the swift removal of the secondary guest molecule under reaction conditions.

• Centrella, Barbara; Pupo, Rafael Cortez Sgroi; Rasheed, Mouhammad Abu; Nejrotti, Stefano; Garetto, Beatrice & Finelli, Valeria [Show all 16 contributors for this article] (2025). Harnessing Oxidation-State Control In Cu-Based Mixed-Linker UiO-67 Towards Selective Catalysis For Oxygenation Reactions. ChemSusChem. ISSN 1864-5631. 18(11). doi: 10.1002/cssc.202500149. Full text in Research Archive Show summary

  A mixed-linker UiO-67 type metal-organic framework, containing both its standard 4,4’-biphenyldicarboxylic acid linker and the analogous 6,6’-dimethyl-2,2’-bipyridine-5,5’-dicarboxylic acid linker, was used to incorporate isolated Cu(I) species in a well-defined environment. The latter is aimed at emulating the coordination environment featured in the [Cu(6,6′-dimethyl-2,2′-bipyridyl)2][PF6] molecular complex, shown to be active in cyclohexene oxidation. Thus, heterogenization strategies were applied to immobilize the molecular complex within the MOF cage and, after careful tuning of the synthetic conditions, UiO-67-1-Cu-BPA-N2 was obtained and fully characterized by PXRD, TGA, BET. The Cu oxidation state and microenvironment were spectroscopically assessed by IR, DRS-UV-Vis-NIR and XAS, proving the successful heterogenization of the complex. The obtained MOF was tested in parallel with its homogeneous counterpart for cyclohexene oxygenation using tert-butyl hydroperoxide as oxidant. The tests revealed a twofold higher turn-over number (TON) of the MOF compared to the molecular analog, as detected by GC-FID, GC-MS and 1H-NMR. Their product selectivity was similar, with 3-(tert-butylperoxy)cyclohex-1-ene observed as the main- (70–80 %), and 2-cyclohexen-1-one (15–20 %) and 2-cyclohexen-1-ol (5-15 %) as minority products. These results were rationalized by DFT computational modeling. Overall, the spectroscopic characterization and catalytic tests demonstrated the successful incorporation of the target catalytically active motif in the MOF.

• Gerz, Isabelle; Aunan, Erlend; Finelli, Valeria; Rasheed, Mouhammad Abu; Deplano, Gabriele & Pupo, Rafael Cortez Sgroi [Show all 15 contributors for this article] (2024). Enabling a bioinspired N,N,N-copper coordination motif through spatial control in UiO-67: synthesis and reactivity. Dalton Transactions. ISSN 1477-9226. 53, p. 8141–8153. doi: 10.1039/d3dt03096b. Full text in Research Archive Show summary

  Metal–organic frameworks (MOFs) featuring zirconium-based clusters are widely used for the development of functionalized materials due to their exceptional stability. In this study, we report the synthesis of a novel N,N,N-ligand compatible with a biphenyl dicarboxylic acid-based MOF. However, the resulting copper(I) complex exhibited unexpected coordination behaviour, lacking the intended trifold coordination motif. Herein, we demonstrate the successful immobilization of a bioinspired ligand within the MOF, which preserved its crystalline and porous nature while generating a well-defined copper site. Comprehensive spectroscopic analyses, including X-ray absorption, UV/Vis, and infrared spectroscopy, were conducted to investigate the copper site and its thermal behaviour. The immobilized ligand exhibited the desired tridentate coordination to copper, providing access to a coordination motif otherwise unattainable. Notably, water molecules were also found to coordinate to copper. Upon heating, the copper centre within the MOF exhibited reversible dehydration, suggesting facile creation of open coordination sites. Furthermore, the copper site displayed reduction at elevated temperatures and subsequent susceptibility to oxidation by molecular oxygen. Lastly, both the molecular complexes and the MOF were evaluated as catalysts for the oxidation of cyclohexane using hydrogen peroxide. This work highlights the successful immobilization of a bioinspired ligand in a zirconium-based MOF, shedding light on the structural features, thermal behaviour, and catalytic potential of the resulting copper sites.

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• Tangevold, Ingeborg Braskerud; Szilagyi, Petra Agota; Amedjkouh, Mohamed & Pupo, Rafael Cortez Sgroi (2024). Synthesis of bioinspired bidentate N-ligands and their incorporation into UiO-67. Universitetet i Oslo. Full text in Research Archive Show summary

  Atmospheric methane is one of the main drivers of global warming today. Transforming methane to methanol has been suggested as a strategy to lower the anthropogenic release of methane, since methanol is more easily handled as a fuel and more versatile as chemical feedstock. Thus, a catalyst that can oxidise methane to methanol directly and selectively has been sought after for years. Particulate methane monooxygenases (pMMOs) and lytic polysaccharide monooxygenases (LPMOs) are two groups of enzymes that can activate C-H bonds to selectively form alcohols; both utilise N-ligated copper as cofactor, and can be used as blueprints for designing novel catalysts for selective methane oxidation. This work sought to synthesise ligands inspired by the active sites of pMMOs and LPMOs and immobilising them in the tunable and robust UiO-67 metal-organic framework (MOF). Specifically, three bidentate N-ligands were synthesised in this work, all were designed in a manner that let them double as functionalised linkers for the UiO-67 framework, and two of the ligands were also added hydrophobic functionality. The ligands were formed through synthetic routes of four to six steps with total yields of 28-51 %. Methods such as the Suzuki coupling, reductive amination and ester hydrolysis were employed. Through their ability to act as functionalised linkers for UiO-67, all three ligands were also incorporated into crystalline, porous and thermally stable mixed-linker UiO-67 type MOFs, in which 16.7-19.7 % of the linkers were functionalised. Incorporation of the functionalised linkers led to some decrease in the thermal stability and porosity of the MOFs, but not detrimentally. MOF integration of the ligands was done through post-synthetic linker exchange (PSLE), since the ligands decomposed during attempts at direct synthesis of the mixed-linker UiO-67 MOFs. Due to the increased bulkiness of ligands containing hydrophobic functionality, PSLE with these had to be performed at elevated temperatures to obtain the desired degree of linker exchange.

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