Pd-modified metal organic frameworks (MOFs) made by mechanochemical extrusion for cross-coupling and electrochemical hydrogen evolution reactions

Mechanochemistry via extrusion is emerging as a powerful and sustainable strategy for the synthesis of advanced materials and for driving chemical transformations under solvent-minimized conditions. In this thesis we report the mechanochemical preparation of zirconium-based Metal-Organic Frameworks (MOFs) (UiO-66, UiO-66-NH2, and MOF-801) functionalized with palladium, using a continuous-flow twin-screw extrusion process, demonstrating its potential for scalable catalyst fabrication. Compared to traditional solution-based routes, extrusion enables continuous processing and improved sustainability. The physicochemical, structural, and morphological characteristics of the obtained materials were investigated through a multi-technique approach, including XPS, XRD, HR-TEM, and N2 physisorption. The analyses confirmed both the effective formation of the MOF structures through the mechanochemical route and the successful incorporation of quasi-spherical palladium nanoparticles, whose dispersion is strongly influenced by the functional groups of the parent MOFs, with UiO-66-NH2 providing superior stabilization. The catalytic performance of the materials was evaluated in two distinct and industrially relevant chemical transformations: (i) the Suzuki-Miyaura cross-coupling reaction and (ii) the electrochemical hydrogen evolution reaction (HER). For the Suzuki-Miyaura reaction, after an initial screening of the catalysts, a full optimization of reaction parameters -temperature, reaction time, and catalyst loading- was conducted. This allowed the identification of conditions outperforming many commonly reported in the literature, leading to significantly enhanced TOFs and meeting important sustainability benchmarks as defined by the CHEM21 First Pass criteria. Furthermore, the catalysts performed effectively across a substrate scope encompassing both aryl bromides and the more challenging aryl chlorides, demonstrating the robustness and applicability of the extruded Pd@MOFs in practical cross-coupling chemistry. Catalyst recycling experiments showed that the materials maintained most of their catalytic activity over multiple cycles, confirming their structural stability and operational durability. An additional attempt was made to apply the materials to the Buchwald–Hartwig cross-coupling amination; while the Pd@MOFs did not deliver satisfactory results. Nonetheless, a commercial Pd/C catalyst enabled the optimization of this reaction affording almost quantitative yields thus offering a promising heterogeneous alternative to traditional homogeneous systems. In the context of HER, the extruded materials showed promising electrocatalytic behaviour. The presence of finely dispersed Pd nanoparticles provided a high density of accessible active sites for proton adsorption during the Volmer step, facilitating efficient hydrogen generation. Among all the investigated systems, 5Pd@UiO-66-NH2-2-200 emerged as the most active HER catalyst. This result is attributed to the -NH2 functional groups, which not only help stabilize small Pd entities but also generate a more electron-rich microenvironment. This electronic modulation enhances the intrinsic kinetic rate (j₀), leading to improved HER performance compared to Pd@MOFs based on fumaric or terephthalic linkers. Overall, this work demonstrates that extrusion-based mechanochemistry offers a sustainable, versatile, and scalable platform for designing and synthetising multifunctional Pd@MOF catalysts. The ability of a single family of materials to perform efficiently in both cross-coupling chemistry and energy-related applications highlights the tunability of this synthetic approach and underscores its potential for broader use in green synthesis, catalysis, and renewable energy technologies.