Ammonia (NH3) plays a crucial role in the low-carbon economy as a promising carrier molecule to supply hydrogen (H2). However, the traditional thermal NH3 decomposition demands temperatures as high as 500-550oC, highlighting its controversiality for energy production. To address this challenge, photo-thermal catalysis arises offering a green pathway to promote the NH3 cracking using sunlight as its unique driving force. In this work, we demonstrate the use of a MOF-derived photo-thermal catalyst for the continuous production of H2 from NH3 under mild conditions, and with no external heating added. Under optimal conditions, a conversion rate of approximately 80% was reached, with no deactivation sign. The synergistic effect of light and heat was evaluated by performing mechanistic studies.

The ability to construct C(sp3)?C(sp3) bonds from easily accessible reagents is a crucial, yet challenging endeavor for synthetic organic chemists. Herein, we report the realization of such a cross-coupling reaction, which combines N-sulfonyl hydrazones and C(sp3)?H donors through a diarylketone-enabled photocatalytic hydrogen atom transfer and a subsequent fragmentation of the obtained alkylated hydrazide. This mild and metal-free protocol was employed to prepare a wide array of alkyl-alkyl cross-coupled products and is tolerant of a variety of functional groups. The application of this chemistry further provides a preparatively useful route to various medicinally-relevant compounds, such as homobenzylic ethers, aryl ethyl amines, ?-amino acids and other moieties which are commonly encountered in approved pharmaceuticals, agrochemicals and natural products.

The development of methods to access alcohol derivatives is one of the main concerns of considerable research. Herein, we report a reductive cross-coupling reaction of ?-oxy halides, simply generated from aldehydes, with a series of C(sp2) and C(sp)-electrophiles. A wide range of aryl and heteroatom aryl halides, vinyl bromides, alkynyl bromides, and acyl chlorides react with unhindered and hindered aldehyde-derived ?-oxy halides by providing protected alcohols as well as ?-hydroxy ketones. Noteworthy, the reductive couplings are achieved not only through thermal catalysis with the use of metal reductants but also by photocatalysis, electrochemistry, and mechanochemistry. The unrestricted interchange of the four strategies indicates their underlying mechanistic similarities. The generation of NiI intermediate is proposed to be the key point for ketyl radical formation via a single electron transfer (SET) event, which was rationalized by an array of control experiments and density functional theory (DFT) calculations.

Electrocatalytic synthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e- ORR) provides a promising alternative to the traditional energy-intensive anthraquinone process, allowing for clean, sustainable, and decentralized H2O2 production. However, developing inexpensive, highly active, and selective catalysts is still a challenge for the electroproduction of H2O2. Here, we engineer large-scale electrocatalysts based on metal-free carbon nanofibers with a fluorine and sulfur dual-doping strategy. Optimized samples yield an onset potential of 0.814 V versus reversible hydrogen electrode (RHE) and a near-unity H2O2 selectivity of 99.1%, superior to most reported carbon/metal-based counterparts. Experimental and theoretical computation results demonstrate that the manipulated free energy profiles and reduced energy barrier of the reaction route stem from the synergistic effect of intermolecular charge transfer coupled with electron spin redistribution after suitable F and S dual-doping, contributing to enhanced performances. This technique paves the way for the design and implementation of sustainable, large-scale, and highly efficient catalysts for the electroproduction of H2O2 and enjoys versatility in other catalytic fields, such as CO2 reduction, water splitting, and ammonia production.

A common issue in chemical processes is that their operation is limited by mass and heat transfer.One example is the uncontrolled increase of temperature for exothermic reactions, generating hotspots, which may damage the reactor structure [1]. Recently, the boost of new manufacturing technologies has permitted the catalysis area to go beyond, and test more complex reactor designs.Additive manufacturing (AM), also known as 3D printing, can significantly contribute to process intensification of unitary processes removing heat and mass transfer limitations [2]. 3D printing allows fabricating free-form sophisticated designs of units like chemical reactors that can be customized to maximize productivity of specific chemistry. Our group uses a lithographic AM method for printing across scales in polymers, metals, ceramics, and their composites in a commercially ready viable way to produce milli-reactors [3]. This platform provides enormous freedom for materials and designs of the next-generation multiscale structured metallic reactors. Fractals are a special group of space-filling curves (SFC). They are infinite self-repeating patterns, and their concept can be used to describe some natural structures, e.g., ferns, trees, and the seacoast [4]. Recently, the utilization of space-filling curves (as well as other geometries) has been revisited for reactor design, as AM can overcome economic manufacturing constraints. SFC curves have the potential to offer compact, and high-volume reactors, offering the possibility to decrease mass and heat transfer limitations, and different mixing levels [5]. A typical fractal reactor designed using a 2D Hilbert-curve is shown in Figure 1.Figure 1. Fractal reactor using Hilbert curve 3D printed in polymer (a) and metal (b).2 The same approach can be used to design other unitary processes like separation vessels. Additionally, reactor internals can be optimized in the same manner to customize heat transfer or/and pressure drop. This approach can be done using lattices [6], triple periodical minimal surfaces (TPMS) [7] or new structures with imprinted porosity that result from the combination of lattices and TPMS solids [8]. Examples of these novel designs and their manufacture in stainless steel are shown in Figure 2. In this work, we will show the recent progress of our group in this area. Results of residence time distribution of different fractal reactors manufactured with the 2D Hilbert curve will be shown for different designs with a fixed volume. Apart from fractal reactors, pressure drop and thermal field across TPMS structures with imprinted porosity will be shown. The pressure drop and heat transfer across TPMS structures with different topologies were determined by CFD simulations under varying operating conditions. In summary, independent on the application target, the uniqueness of this fully digital approach is that the CAD design of the reactor can be used for assessing its performance, adapting the shape of the reactor until the specified KPIs are satisfied. Only at the point where the desired result is obtained, the reactor can be physically manufactured. Our main target is to contribute to the generation of intensified chemical reactors with milli-scale dimensions, where shape customization can enable the production of targeted chemicals, especially under demanding conditions or in challenging environments [9]. References: [1] Cambie, D., Bottecchia, C., Straathof, N. J., Hessel, V., & Noel, T., Applications of continuous-flow photochemistry in organic synthesis, material science, and water treatment. Chemical reviews, 2016, 10276-10341. [2] Stankiewicz, Andrzej I., and Jacob A. Moulijn. (Process intensification: transforming chemical engineering.)Chemical engineering progress, 2000, 22-34.3 [3] Melentiev R., Harakály G., Stögerer J., Mitteramskogler G., Grande C., Lithography Metal Additive Manufacturing. Additive Manufacturing, 2023 (Submitted). [4] Prusinkiewicz, Przemyslaw, and Aristid Lindenmayer. The algorithmic beauty of plants. Springer Science & Business Media, 2012. [5] Grande, C., Compact reactor architectures designed with fractals. Reaction Chemistry & Engineering, 2021,1448-1453. [6] Rebelo, N. F. B.; Andreassen, K. A.; Rios, L. I. S.; Camblor, J. C. P.; Zander, H. J.; Grande, C. A., Pressure drop and heat transfer properties of cubic isoreticular foams. Chemical Engineering and Processing-Process Intensification, 2018, 36-42. [7] Zimmer, Arthur, et al. Effect of manufacturing techniques in pressure drop on triple periodical minimal surface packings. Chemie Ingenieur Technik, 2021, 967-973. [8] Asif, M.; Grande, C. A., TPMS Contactors Designed with Imprinted Porosity: Numerical Evaluation of Momentum and Energy Transport. Industrial & Engineering Chemistry Research, 2022, 18556-185. [9] Grande, Carlos A., and Terje Didriksen. Production of Customized Reactors by 3D Printing for Corrosive and Exothermic Reactions. Industrial & Engineering Chemistry Research, 2021, 16720-16727.

The traditional Staudinger/aza-Wittig reaction represents one of the most powerful tools for imine formation. However, for this multistep procedure, the sacrificial phosphine has to be used, resulting in difficulties in the purification process and waste disposal at the same time. Here, we report a redox-neutral azide-alcohol imination methodology enabled by a base-metal nickel PN3 pincer catalyst. The one-step, waste-free, and high atom-economical features highlight its advantages further. Moreover, mechanistic insight suggests a non-metal-ligand cooperation pathway based on the observation of intermediate and density functional theory calculations.

We herein report an unconventional Ni-catalyzed cascade reaction of 2-alkynyl phenol ester with boronic acid that incorporates an arylation of alkynes induced acyl group migration to produce tetra substituted functionalized alkenes in good-to-excellent yields with exclusive E-selectivity. Mechanistically, the transformation involves the generation of a nucleophilic vinyl Ni(II) species by the regioselective syn-aryl nickelation of an alkyne, which undergoes an intramolecular acyl migration with tether phenol ester to yield highly functionalized acyclic tetra-substituted alkenes. The steric and electronic trialkyl phosphine ligand is crucial for providing high regio- and stereocontrolled for efficient migratory carbo-acylation of alkynes. Finally, the synthetic utility of the obtained products is also demonstrated.