A novel and advantageous protocol for accessing carbamates through the known three-component coupling reaction involving carbon dioxide, amines, and alkyl halides is described. Employing mild conditions, simple experimental set-up, and immobilized DBU, this protocol addresses several drawbacks from the previous described methods. No classical purification procedures are necessary and the immobilized DBU can be recycled and reused several times.

Abstract

The present study highlights a novel and advantageous protocol for accessing carbamates through the well-established three-component coupling reaction involving CO₂, amines, and alkyl halides. By employing an immobilized organic base, operating under mild reaction conditions, an array of alkyl carbamates in yields of up to 95 % could be isolated. This approach offers a broad and versatile product scope, allowing for the facile modification of both the amine and alkyl halide reactants. Notably, the pioneering use of an immobilized organic base, specifically the polymer-supported 1,8-diazabicyclo[5.4.0]undec-7-ene (PS-DBU), in this three-component reaction eliminates the need for classical purification steps, streamlining the process. To ensure practicality and sustainability, extensive studies were conducted to verify the recovery and reusability of the polymer-supported DBU catalyst, which consistently maintained the high chemical yield of the carbamates across multiple cycles. Overall, this innovative protocol represents a significant advancement in carbamate synthesis, combining efficiency, generality, and the potential for DBU recycling.

A robust method to determine degradation rates of an amine functionalized polystyrene adsorbent in a laboratory setup is developed and validated with a continuous multi-staged fluidized bed pilot plant. The very good agreement between experimental 1000-hour laboratory and 2200-hour pilot degradation showcases how small scale experiments can be extrapolated for scale-up and adsorbent screening.

Abstract

Alternative to current liquid amine technologies for post-combustion CO₂ capture, new technologies such as adsorbent-based processes are developed, wherein material lifetime and degradation is important. Herein a robust method to determine degradation rates in a laboratory setup is developed, which was validated with a continuous multi-staged fluidized bed pilot plant designed to capture 1 ton CO₂ per day. An amine functionalized polystyrene adsorbent showed very good agreement between the experimental 1000-hour laboratory degradation rates and 2200 hours of degradation in a pilot plant. This validates how laboratory experiments can be extrapolated for sorbent screening and for scale-up. Resulting, the oxidative degradation in the desorber at high temperatures (120 °C) and low O₂ concentrations (150 ppmv) is 3 times higher compared to the adsorber at low temperatures and high O₂ (56 °C, 7 vol %). Laboratory degradation experiments can hence be used to further optimize process operations to limit degradation or screen for potential new adsorbents.

The first enantioselective reduction of 2-substituted cyclic imines to the corresponding amines (pyrrolidines, piperidines, and azepines) by imine reductases (IREDs) in non-conventional solvents is reported. The best results were obtained in a glycerol/phosphate buffer 1:1 mixture, in which heterocyclic amines were produced with full conversions (>99%), moderate to good yields (22-84%) and excellent S-enantioselectivities (up to >99% ee). Remarkably, the process can be performed at a 100 mM substrate loading which, for the model compound, means a concentration of 14.5 g/L. A fed-batch protocol was also developed for a convenient scale-up transformation and one millimol of substrate 1a was readily converted into 120 mg of enantiopure amine (S)-2a with a remarkable 80% overall yield. This aspect strongly contributes in making the process potentially attractive for large scale applications in terms of economic and environmental sustainability to a discrete number of substrates to produce enantiopure cyclic amines of high pharmaceutical interest.

Electrochemical conversion of underutilized biomass-based glycerol into high-value-added products provides a green approach for biomass and waste valorization. Plus, this approach offers an alternative to biofuel manufacturing procedure, under mild operating conditions, compared to the traditional thermochemical routes. Nevertheless, glycerol has been widely valorized via electrooxidation, with lower-value products generated at the cathode, ignoring the electroreduction. Here we study and establish a review of the efficient glycerol reduction into various products via the electrocatalytic reduction (ECR) process. This review has been built upon the background of glycerol underutilization and theoretical knowledge about the state-of-the-art ECR. The experimental understanding of the processing parameter influences towards electrochemical efficiency, catalytic activity, and product selectivity are comprehensively reviewed, based on the recent glycerol ECR studies. We conclude by outlining present issues and highlighting potential future research avenues for enhanced ECR application.

Molecular solar thermal (MOST) energy storage systems are getting increased attention related to renewable energy storage applications. Particularly, 2,3-difunctionalized norbornadiene-quadricyclane (NBD-QC) switches bearing a nitrile (CN) group as one of the two substituents are investigated as promising MOST candidates thanks to their high energy storage densities and their red-shifted absorbance. Moreover, such NBD systems can be prepared in large quantities (a requirement for MOST-device applications) in flow through Diels-Alder reaction between cyclopentadiene and appropriately functionalized propynenitriles. However, these acetylene precursors are traditionally prepared in batch from their corresponding acetophenones using reactive chemicals potentially leading to health and physical hazards, especially when working on a several-grams scale. Here, we develop a multistep flow-chemistry route to enhance the production of these crucial precursors. Furthermore, we assess the atom economy (AE) and the E-factor showing improved green metrics compared to classical batch methods. Our results pave the way for a complete flow synthesis of NBDs with a positive impact on green chemistry aspects.

La−TM−Si electrides catalysts for ammonia synthesis were compared and different catalytic mechanisms were shown for LaFe/CoSi and LaMnSi. A dual-site relay catalytic mechanism was demonstrated for LaCoSi and LaFeSi, breaking the scaling relations. In contrast, all the elementary steps were confined to Mn sites on LaMnSi, which resulted in inferior catalytic activity.

Abstract

Intermetallic electrides have recently drawn considerable attention due to their unique electronic structure and high catalytic performance for the activation of inert chemical bonds under mild conditions. However, the relationship between electride (anionic) electron abundance and catalytic performance is undefined; the key deciding factor for the performance of intermetallic electride catalysts remains to be addressed. Here, the secret behind electride catalysts La−TM−Si (TM=Co, Fe and Mn) with the same crystal structure but different anionic electrons was studied. Unexpectedly, LaCoSi with the least anionic electrons showed the best catalytic activity. The experiments and first-principles calculations showed that the electride anions promote the N₂ dissociation which alters the rate-determining step (RDS) for ammonia synthesis on the studied electrides. Different reaction mechanisms were found for La−TM−Si (TM=Fe, Co) and LaMnSi. A dual-site module was revealed for LaCoSi and LaFeSi, in which transition metals were available for the N₂ dissociation and La accelerates the NH _x formation, respectively, breaking the Sabatier scaling relation. For LaMnSi, which is the most efficient for the N₂ activation, the activity for ammonia synthesis is limited and confined by the scaling relations. The findings provide new insight into the working mechanism of intermetallic electrides.

The significant rise in end-of-life tires (ELTs) globally poses immediate environmental and human health risks. Therefore, to promote ELTs recycling and to reduce tire industry carbon emissions, herein we present a facile approach for fine-tuning the interfacial interactions between pyrolytic carbon black (P-CB) obtained from ELTs and natural rubber (NR)  using phosphonium-based ionic liquid (PIL). The reinforcing effect of PIL-activated P-CB was studied by replacing the furnace-grade carbon black (N330-CB) with varying PIL and P-CB loadings. Adding PIL improved the filler dispersion and the cross-linking kinetics with a substantially reduced zinc oxide  loading. Considering the cross-linking and viscoelastic properties, it was concluded that the composite, P-CB/N330-CB-PIL (1.5) + ZnO (1) with half substitution of N330-CB with P-CB synergistically works with 1.5 phr PIL and 1 phr of ZnO resulting in improved dynamic-mechanical properties with a minimal loss tangent  at 60 °C (tanδ = 0.0689) and improved glass transition temperature (Tg = - 38 °C) compared to control composite. The significant drop (~ 29 % lower) in tanδ could reduce fuel consumption and related CO2 emissions. We envisage that this strategy opens an essential avenue for “Green Tire Technology” towards the substantial pollution abatement from ELTs and reduces the toxic ZnO.

Electrochemical water splitting to generate hydrogen energy fills a yawning gap in the intermittency issues for wind and sunlight power. Transition metal (TM) oxides have attracted significant interest in water oxidation due to their availability and excellent activity. Typically, the transitional metal oxyhydroxides species derived from these metal oxides are often acknowledged as the real catalytic species, due to the irreversible structural reconstruction. Hence, in order to innovatively design new catalyst, it is necessary to provide a comprehensive understanding for the origin of surface reconstruction. In this work, the most recent developments in the reconstruction of transition metal-based oxygen evolution reaction electrocatalysts were introduced, and various chemical driving forces behind the reconstruction mechanism were discussed. At the same time, specific strategies for modulating pre-catalysts to achieve controllable reconfiguration, such as metal substituting, increase of structural defect sites, were summarized. At last, the issues for the further understanding and optimization of transition metal oxides compositions based on structural reconstruction were provided.

The utilization of water as a sustainable reaction medium has important advantages over traditional organic solvents. Hydroxypropyl methylcellulose has emerged as a biomass-based polymeric additive that enables organic reactions in water through hydrophobic effects. However, such conditions imply slurries as reaction mixtures, where the efficacy of mass transfer and mixing decreases with increasing vessel size. In order to circumvent this limitation and establish an effectively scalable platform for performing hydroxypropyl methylcellulose-mediated aqueous transformations, we utilized oscillatory plug flow reactors that feature a smart dimensioning design principle across different scales. Using nucleophilic aromatic substitutions as valuable model reactions, rapid parameter optimization was performed first in a small-scale instrument having an internal channel volume of 5 mL. The optimal conditions were then directly transferred to a 15 mL reactor, achieving a three-fold scale-up without re-optimizing any reaction parameters. By precisely fine-tuning the oscillation parameters, the system achieved optimal homogeneous suspension of solids, preventing settling of particles and clogging of process channels. Ultimately, this resulted in a robust and scalable platform for performing multiphasic reactions under aqueous conditions.

Graphdiyne catalysts for ammonia synthesis! This review highlights the unique structures and properties of graphdiyne, provides a comprehensive update in regard to the synthesis of graphdiyne-based multiscale catalysts and their applications in the synthesis of ammonia, and discusses the challenges and future perspectives relating to graphdiyne.

Abstract

Graphdiyne, a sp/sp²-cohybridized two-dimensional all- carbon material, has many unique and fascinating properties of alkyne-rich structures, large π conjugated system, uniform pores, specific unevenly-distributed surface charge, and incomplete charge transfer properties provide promising potential in practical applications including catalysis, energy conversion and storage, intelligent devices, life science, photoelectric, etc. These superior advantages have made graphdiyne one of the hottest research frontiers of chemistry and materials science and produced a series of original and innovative research results in the fundamental and applied research of carbon materials. In recent years, considerable advances have been made toward the development of graphdiyne-based multiscale catalysts for nitrogen fixation and ammonia synthesis at room temperatures and ambient pressures. This review aims to provide a comprehensive update in regard to the synthesis of graphdiyne-based multiscale catalysts and their applications in the synthesis of ammonia. The unique features of graphdiyne are highlighted throughout the review. Finally, it concludes with the discussion of challenges and future perspectives relating to graphdiyne.