Chem最新文献

Replacement of the oxygen evolution reaction (OER) by energetically more favorable electrooxidation reactions opens up an innovative pathway for energy-saving hydrogen (H₂) production. In particular, the electrooxidation of biomass molecules, plastic wastes, and organic compounds has attracted escalating interest in recent years, owing to its potential for simultaneous H₂ production at the cathode and value-added chemical and fuel generation at the anode. This review article does not aim to provide a comprehensive overview of these reactions but rather to highlight the key advancements in the strategies of reaction design, activity enhancement, and selectivity regulation based on the features and challenges in each type of reaction. Through this review of key advancements, we offer mechanistic insights that guide the design of more efficient coupling systems. Lastly, the challenges and future prospects in this field are discussed.

Although non-noble metal catalysts are appealing for propane dehydrogenation, achieving high propylene selectivity remains a persistent challenge, which necessitates the regulation of catalytic microenvironment. In this study, we comparatively investigate three commonly used active metals (Pt, Pd, and non-noble metal Ni) using both theoretical and experimental approaches. We find that the low selectivity of Ni-based catalysts is intrinsically attributed to a narrow interatomic distance (Δd) between Ni atoms, which promotes side reactions. Thus, Ni-based intermetallic alloys are employed to modulate Δd, whose surface microenvironment is quantified with a descriptor called degree-of-isolation. The established volcano-shaped isolation-selectivity plot provides a direct avenue for predicting propylene selectivity, which is determined by two competing variables: desorption and further dehydrogenation of propylene. The optimal catalyst, NiIn, manifests moderate Ni–C repulsion, obtaining >91% experimental propylene selectivity. This reveals the Sabatier principle over Ni-based catalysts for selective propane dehydrogenation and underscores the significance of microenvironment engineering.

Various studies have hypothesized that life on Earth may have originated near seafloor, mineral-rich hydrothermal vents. The use of laboratory analogs of these environments, such as chemical gardens, allows the creation of controlled, manipulable systems for studying potential prebiotic chemistry and origins-of-life scenarios on Earth and beyond. In this study, we tested reactions of prebiotically relevant organic anions, pyruvate and glyoxylate, in the presence of chemical gardens under a set of conditions relevant to the early Earth and the Saturnian moon Enceladus. Reactions were run for up to 3 weeks and then analyzed. Prebiotically relevant molecules were synthesized from organics reacted in the presence of chemical gardens under early-Earth-like conditions. As our reactants are readily available in geological settings, it is possible that similar self-organized structures could have played a role in prebiotic chemistry on early Earth or potentially even on other ocean-containing places in the solar system.

N-heterocyclic carbenes (NHCs) have recently proven to be powerful ligands for planar surface modification in terms of chemical and electronic properties due to their structural diversity, property tunability, and high affinity for a diverse array of elements. However, the utilization of NHCs for planar surface modification has almost exclusively been limited to bulk substrates. Here, we investigate the adsorption of NHCs on a two-dimensional (2D) metal (i.e., borophene) using combined single-molecule optical/electronic spectroscopy. Tip-enhanced Raman spectroscopy reveals two distinct interfacial states between individual NHCs and borophene, which correspond to covalent (boron–carbon bonding) and van-der-Waals-type interactions. Furthermore, the impact of NHC modification on borophene’s electronic properties is demonstrated by local work function reductions, as measured by scanning tunneling spectroscopy. In addition to providing novel insight into NHC–substrate interactions in the 2D regime, this study opens up an avenue for investigations of single-molecule NHC chemistry.

New mechanisms that transduce chemical potential into work are needed to advance the field of nanotechnology, with the ATP-fueled archaeal flagellar rotational motor being the ultimate inspiration. We describe microns-long ribbons assembled from small peptides that catalyze the conversion of a nanometer-sized molecular fuel. This conversion drives a morphological transition of the flat nanoribbons into helical ones and eventually into tubes, which makes the ribbons spin. Remarkably, the spinning speed and directionality can be tuned by molecular design. Moreover, the nanoribbons exert pN forces on their surroundings, allowing them to push micron-sized objects or even crawl. Our work demonstrates a new mechanism by which chemical energy at the nanometer level is used to power micron-sized machinery. We envision such new mechanisms opening the door to micro- and nanoscale autonomous machines.

Kinetic asymmetry is a key parameter describing non-equilibrium systems: it indicates the directionality of a reaction network under steady-state conditions. So far, kinetic asymmetry has been evaluated only in networks featuring a single cycle. Here, we have investigated kinetic asymmetry in a multi-cycle system using a combined theoretical and numerical approach. First, we report the general expression of kinetic asymmetry for multi-cycle networks. Then, we specify it for a recently reported electrochemically controlled network comprising diffusion steps, which we used as a model system to reveal how key parameters influence directionality. In contrast with the current understanding, we establish that spatial separation—including compartmentalization—can enable autonomous energy ratchet mechanisms, with directionality dictated by thermodynamic features. Kinetic simulations confirm analytical findings and illustrate the interplay between diffusion, chemical, and electrochemical processes. The treatment is general, as it can be applied to other multi-cycle networks, facilitating the realization of endergonic processes across domains.

Inspired by natural systems, metal-organic cages with well-defined shapes and cavities can be tuned for different guest-binding functions. Here, we report the construction of two types of cage frameworks: an M^II₁₂L₈ (M = Zn^II and Co^II) pseudo-cuboctahedral architecture 1 and a rarer M^II₉L₈ (M = Zn^II and Co^II) pseudo-Johnson-solid-type (J₅₁) framework 2. Both structures form from the same boron-containing triamine subcomponent, and each one incorporates hexacoordinate metal vertices chelated by only two bidentate pyridyl(imine) arms. Such vertices provide the cages with the flexibility required to form lower-symmetry architectures, and they also facilitate reversible disassembly in response to fluoride. These cages were also shown to respond to other chemical stimuli enabling transformation between cage structures. Cage 1 bound different guest molecules, including the anticancer drug paclitaxel, C-methylcalix[4]resorcinarene, and tetraphenylborates. The release of paclitaxel by 1 was stimulated by fluoride or chloride, highlighting the potential for applications in natural product separation and drug delivery.