Search

The reduction of CO2 into higher energy products such as carbon-based fuels and feedstocks is an attractive strategy for mitigating the continuous rise in CO2 emissions associated with the growing global energy demand. Rhenium tricarbonyl complexes bearing 2,2′-bipyridine (2,2′-bpy) ligands are well-established molecular electrocatalysts for the selective reduction of CO2 to CO. Construction of efficient devices for this electrochemical process requires the immobilization of electrocatalysts to electrode surfaces. To integrate Re(2,2′-bpy)(CO)3 fragments into a covalent organic framework (COF), Re(5,5′-diamine-2,2′-bpy)(CO)3Cl (1) was synthesized and electrochemically investigated. Complex 1 is an active and selective electrocatalyst for the reduction of CO2 to CO with excellent faradaic efficiency (99%). The presence of the amine substituents leads to a destabilization of the π* orbital of the 5,5′-diamine-2,2′-bpy ligand with respect to the metal center. Therefore, 1 requires more negative potentials (−2.47 V vs. Fc+/0) to reach the doubly reduced catalytically active species. DFT studies were conducted to understand the electronic structure of 1, and support the destabilizing effect of the amine substituents. The Re-2,2′-bpy fragments were successfully integrated into a COF containing 2,2′-bpy moieties (COF-2,2′-bpy) via a post-metallation synthetic route to generate COF-2,2′-bpy-Re. A composite of COF-2,2′-bpy-Re, carbon black, and polyvinylidene fluoride (PVDF) was readily immobilized onto glassy carbon electrodes and electrocatalytic CO2 reduction to CO was observed at −2.8 V vs. Fc0/+, with a faradaic efficiency of 81% for CO production. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) effectively alleviates pain for pediatric patients during many medical procedures, such as venipuncture and burn care. In our previously published randomized clinical trial among 90 pediatric burn patients, participants in the active VR group had significantly lower scores for overall pain compared with participants in the standard care control and for worst pain compared with participants in the passive VR and control group. However, whether VR differs by a patient's age or sex remains unresolved. Thus, we reanalyzed our data by comparing the active and passive VR participants to evaluate how age and sex affect VR pain alleviation during dressing care for pediatric burns. In total, 90 patients aged 6-17 years (inclusive) with burn injuries were recruited from an outpatient burn clinic of an American Burn Association-verified pediatric burn center. Before randomization, VR helpfulness and need expectations were assessed on a visual analog scale (0-100). Participants were randomly assigned to active VR, passive VR, or control for one dressing change. Immediately following the dressing change, active and passive VR participants self-reported pain and the time spent thinking about pain and rated the VR features on the degree of realism, pleasure/fun, and perceived engagement level. Path analyses assessed how these VR features were interrelated and how they affected self-reported pain by age and sex. Patients aged 6-9 years reported higher mean expectations of VR helpfulness and need (mean = 73.6 and 94.5, respectively) than 10-12-year-olds (mean = 55.7 and 84.2, respectively) and 13-17-year-olds (mean = 68.6 and 77.4, respectively). The path analysis indicated VR engagement and fun were significantly correlated ( p- value < 0.05). VR engagement significantly negatively impacted overall pain scores (coefficient = -0.45, -0.41; p- value < 0.05) and significantly positively impacted time thinking of pain (coefficient = 0.38, 0.32; p- value < 0.05). Younger patients had the highest expectations of VR helpfulness and need. VR game realism, fun, and engagement features were not statistically different between age groups and sexes. VR engagement and thinking of pain during burn dressing significantly positively affected self-reported pain ( p- value < 0.05), suggesting an analgesic mechanism beyond distraction alone. Younger patients benefited more from VR than older patients., (© The Author(s) 2024. Published by Mary Ann Liebert, Inc.)

The design of effective electrocatalysts for carbon dioxide reduction requires understanding the mechanistic underpinnings governing the binding, reduction, and protonation of CO 2 . A critical aspect to understanding and tuning these factors for optimal catalysis revolves around controlling the electronic environments of the primary and secondary coordination sphere. Herein we report a series of para -substituted cobalt aminopyridine macrocyclic catalysts 2 - 4 capable of carrying out the electrochemical reduction of CO 2 to CO. Under catalytic conditions, complexes 2 - 4 , as well as the unsubstituted cobalt aminopyridine complex 1 , exhibit i cat / i p values ranging from 144 to 781. Complexes 2 and 4 exhibit a pronounced precatalytic wave suggestive of an ECEC mechanism. A Hammett analysis reveals that ligand modifications with electron-donating groups enhance catalysis (ρ < 0), indicative of positive charge buildup in the transition state. This trend also extends to the Co I/0 potential, where complexes possessing more negative E (Co I/0 ) reductions exhibit greater i ca t / i p values. The reported modifications offer a synthetic lever to tune catalytic activity, orthogonal to our previous study of the role of pendant hydrogen bond donors.

The bioinspired incorporation of pendant proton donors into transition metal catalysts is a promising strategy for converting environmentally deleterious CO 2 to higher energy products. However, the mechanism of proton transfer in these systems is poorly understood. Herein, we present a series of cobalt complexes with varying pendant secondary and tertiary amines in the ligand framework with the aim of disentangling the roles of the first and second coordination spheres in CO 2 reduction catalysis. Electrochemical and kinetic studies indicate that the rate of catalysis shows a first-order dependence on acid, CO 2 , and the number of pendant secondary amines, respectively. Density functional theory studies explain the experimentally observed trends and indicate that pendant secondary amines do not directly transfer protons to CO 2 , but instead bind acid molecules from solution. Taken together, these results suggest a mechanism in which noncooperative pendant amines facilitate a hydrogen-bonding network that enables direct proton transfer from acid to the activated CO 2 substrate., Competing Interests: The authors declare no competing financial interest.