Zeolite encapsulated metal nanoparticle catalysts hold great promise for several green and sustainable processes, ranging from environmental remediation to renewable energy and biomass conversion. In particular, the microporous zeolite framework keeps the nanoparticles in a firm grip that can control selectivity and prevent sintering at high temperatures. While progress in the synthesis of mesoporous zeolites continues, the encapsulation of metal nanoparticles remains a challenge that often requires complex procedures and expensive additives. Here, we report a general method to encapsulate both base and noble metal nanoparticles inside the internal voids of a compartmentalized mesoporous zeolite prepared by carbon templating and steam-assisted Page 1 of 40 ACS Paragon Plus Environment ACS Applied Nano Materials 2 recrystallization. This results in a remarkable shell-like morphology that facilitates the formation of small metal nanoparticles upon simple impregnation and reduction. When the materials are applied in catalysis, we for instance demonstrate that zeolite encapsulated Ni nanoparticles are highly active, selective and stable catalysts for CO2 methanation (49% conversion with 93% selectivity at 450°C). A reaction where catalysts often suffer from sintering due to the high reaction temperatures. While the introduction of Ni nanoparticles prior to the steam-assisted recrystallization results in the formation of inactive nickel phyllosilicates, noble metals such as Pt do not suffer from this limitation. Therefore, we also demonstrate the synthesis of an active catalyst prepared by the formation of Pt nanoparticles prior to the shell synthesis. We tested the zeolite encapsulated Pt nanoparticles for hydrogenation of linear and cyclic alkenes with increased chain length. The catalysts are active for hydrogenation of oct-1-ene (66% conversion) and cyclooctene (79% conversion) but inactive for the large cyclododecane (<1% conversion), which show that this type of catalyst is highly selective in size selective catalysis. All catalysts are characterized by XRD, TEM, XPS and N2 physisorption.

Heterogeneous immobilized molecular catalysis has gained significant attention as a platform for creating more efficient and selective catalysts. A promising type of immobilized molecular catalysts are made from porous organic polymers (POPs) due to their high stability, porosity, and ability to mimic the catalytic activity and selectivity of homogeneous organometallic catalysts. These properties of the POP‐based systems make them very attractive as heterogeneous catalysts for hydrogenation of CO2 to formate, where predominately homogeneous systems have been applied. In this study, five POPs were synthesized and assessed in the hydrogenation of CO2 where the active catalysts were made in‐situ by mixing IrCl3 and the POPs. One of the Ir/POP catalysts provided a turn‐over number (TON) >20,000, which is among the highest for POP‐based systems. Thorough characterization (CO2‐ and N2‐physisorption, TGA, CHN‐analysis, XRD, XPS, SEM, STEM and TEM) was performed. Notably, the developed Ir/POP system also showed catalytic activity for the decomposition of formic acid into H2 enabling the use of formic acid as a renewable energy carrier.

Selective formic acid dehydrogenation over an efficient RuO2/COF pre-catalyst with good dispersion of the active metal and large N-content on the COF support.

Carbon supported Cu nanoparticles have a remarkable selectivity towards the catalytic dehydrogenation of bioethanol to acetaldehyde, which is an interesting alternative to the preparation from ethylene. In this work, we prepared a series of catalysts comprised of Cu nanoparticles supported on N-doped ordered mesoporous carbons to investigate the catalytic effect of nitrogen content. Our study shows that N-doping has a significant effect on the dispersion of Cu nanoparticles and that the highest content of N results in the highest activity. Furthermore, we show that the combined effects of strong metal-support interactions and nano-confinement is an effective method to prevent thermal and steam induced sintering. In contrast, we find no evidence that N-doping activates the substrate or change the rate-determining step. At 260°C, the best catalyst results in > 99 % selectivity and a site-time yield of 175 mol acetaldehyde /mol Cu /h. Under these conditions, the catalysts are stable for more than 12 h using an aqueous solution of 10 % ethanol as feed.

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