Continuous-flow methodologies offer promising avenues for sustainable processing due to their precise process control, scalability, and efficient heat and mass transfer. The small dimensions of continuous-flow reactors render them highly suitable for light-assisted reactions, as can be encountered in carbon dioxide hydrogenations. In this study, we present a reactor system emphasizing reproducibility, modularity, and automation, facilitating streamlined screening of conditions and catalysts for these processes. The proposed commercially available photoreactor, in which carbon dioxide hydrogenation was conducted, features narrow channels with a high-surface area catalyst deposition. Meticulous control over temperature, light intensity, pressure, residence time, and reagent stoichiometry yielded the selective formation of carbon monoxide and methane using heterogeneous catalysts, including a novel variant of ruthenium nanoparticles on titania catalyst. All details on the automation are made available, enabling its use by researchers worldwide. Furthermore, we demonstrated the direct utilization of on-demand generated carbon monoxide in the production of fine chemicals various carbonylative cross-coupling reactions.

Monoclinic vanadium dioxide (VO (M)) is a promising material for various applications ranging from sensing to signature management and smart windows. Most applications rely on its reversible structural phase transition to rutile VO (VO (R)), which is accompanied by a metal-to-insulator transition. Bottom-up hydrothermal synthesis has proven to yield high quality monoclinic VO but requires toxic and highly reactive reducing agents that cannot be used outside of a research lab. Here, we present a new hydrothermal synthesis method using nontoxic and safe-to-use oxalic acid as a reducing agent for VO to produce VO (M). In early stages of the process, polymorphs VO (A) and VO (B) were formed, which subsequently recrystallized to VO (M). Without the presence of W, this recrystallization did not occur. After a reaction time of 96 h at 230 °C in the presence of (NH)HWO in Teflon-lined rotated autoclaves, we realized highly crystalline, phase pure W-doped VO (M) microparticles of uniform size and asterisk shape (Δ = 28.30 J·g, arm length = 6.7 ± 0.4 μm, arm width = 0.46 ± 0.06 μm). We extensively investigated the role of W in the kinetics of formation of VO (M) and the thermodynamics of its structural phase transition.

The urgent need to reduce the carbon dioxide level in the atmosphere and keep the effects of climate change manageable has brought the concept of carbon capture and utilization to the forefront of scientific research. Amongst the promising pathways for this conversion, sunlight-powered photothermal processes, synergistically using both thermal and non-thermal effects of light, have gained significant attention. Research in this field focuses both on the development of catalysts and continuous-flow photoreactors, which offer significant advantages over batch reactors, particularly for scale-up. Here, we focus on sunlight-driven photothermal conversion of CO to chemical feedstock CO and CH as synthetic fuel. This review provides an overview of the recent progress in the development of photothermal catalysts and continuous-flow photoreactors and outlines the remaining challenges in these areas. Furthermore, it provides insight in additional components required to complete photothermal reaction systems for continuous production (e. g., solar concentrators, sensors and artificial light sources). In addition, our review emphasizes the necessity of integrated collaboration between different research areas, like chemistry, material science, chemical engineering, and optics, to establish optimized systems and reach the full potential of this technology.

This study reports the low temperature and low pressure conversion (up to 160 °C, = 3.5 bar) of CO and H to CO using plasmonic Au/TiO nanocatalysts and mildly concentrated artificial sunlight as the sole energy source (up to 13.9 kW·m = 13.9 suns). To distinguish between photothermal and non-thermal contributors, we investigated the impact of the Au nanoparticle size and light intensity on the activity and selectivity of the catalyst. A comparative study between P25 TiO-supported Au nanocatalysts of a size of 6 nm and 16 nm displayed a 15 times higher activity for the smaller particles, which can only partially be attributed to the higher Au surface area. Other factors that may play a role are e.g., the electronic contact between Au and TiO and the ratio between plasmonic absorption and scattering. Both catalysts displayed ≥84% selectivity for CO (side product is CH). Furthermore, we demonstrated that the catalytic activity of Au/TiO increases exponentially with increasing light intensity, which indicated the presence of a photothermal contributor. In dark, however, both Au/TiO catalysts solely produced CH at the same catalyst bed temperature (160 °C). We propose that the difference in selectivity is caused by the promotion of CO desorption through charge transfer of plasmon generated charges (as a non-thermal contributor).

Reactive surfactants (surfmers), which are covalently attached to the surface of sub-micron sized polymer particles during emulsion polymerisation, are applied to tailor the surface functionality of polymer particles for an application of choice. We present a systematic study on the use of oligoglycidol-functionalised styrene macromolecules as surfmers in the emulsion polymerization of styrene. Firstly, we report the impact of the surfmer concentration on the particle size for polymerisations performed above and below the critical micelle concentration. Secondly, we report the influence of the oligoglycidol chain length on the particle size. Thirdly, we conducted experiments to analyse the influence of the surfmer concentration and its chain length on the colloidal stability of the aqueous polystyrene nanoparticles in sodium chloride solutions. We demonstrated that the size of polystyrene particles could be influenced by changing both the surfmer concentration and its chain length. Furthermore, we showed that the colloidal stability of the oligoglycidol-functionalized polystyrene particles is dependent on the particle size, and not directly related to the oligoglycidol chain length.

Protecting groups are commonly applied in multi-step molecular syntheses to protect one or multiple functional groups from reacting. After the reaction, they are removed from the molecule. In full analogy to this concept, we report the practical and scalable colloidal synthesis of Au semishells using polyphenylsiloxane protecting patches to prevent part of the surface of polystyrene nanoparticles from being covered with Au. After Au deposition, the patches are removed yielding Au semishells. We anticipate that this strategy can be extended to the synthesis of other types of non-centrosymmetric nanoparticles.