Search Results (223)

CO₂ hydrogenation to methanol is achieved by homogeneous catalysts through a formic acid derivative. Previous studies have focused on using large amounts of additives to activate this intermediate, such as strong acids, amines and alcohols. Hydrogenation of CO₂ under basic conditions has been reported to only produce highly stable formate salts. We present in this contribution a novel method for formate activation that allows for CO₂ hydrogenation to methanol under basic conditions, by bimetallic activation of the formate salt by a cobalt and a nickel complex. From various catalytic and stoichiometric experiments, we propose that the nickel catalyst binds the in situ-generated formate to activate it for intramolecular cobalt hydride transfer, leading to an intermediate that can be further hydrogenated to methanol. This strategy could open new avenues in CO₂ hydrogenation under basic conditions, with implications for both homogeneously and heterogeneously catalyzed processes. Full article

The valorisation of lignocellulosic residues into bio-based feedstocks is a key strategy for advancing circular bioeconomy models. In this study, chestnut wood residues, including virgin wood (VW) and detannized wood (DT) from the tannin industry, were evaluated as substrates for polyhydroxyalkanoate (PHA) production using Cupriavidus necator. Biomass was subjected to thermo-acid hydrolysis followed by ion-exchange detoxification, yielding hydrolysates rich in organic acids (levulinic, acetic, and formic acids) and residual inhibitory compounds. Both substrates supported microbial growth and PHA accumulation, although clear differences in performance were observed. The maximum biomass concentration reached 1.26 ± 0.01 g L⁻¹ in VW hydrolysate and 0.40 ± 0.03 g L⁻¹ in DT hydrolysate. PHA production was higher in VW hydrolysate, reaching 68.51 mg L⁻¹ with 5.44% (w/w) accumulation, while DT hydrolysate yielded 0.21 mg L⁻¹ with 6.01% (w/w). The reduced biomass formation in DT hydrolysate was associated with the greater persistence of inhibitory compounds generated during thermo-acid treatment. Although the obtained PHA yields are lower than those reported for optimized lignocellulosic systems, this study demonstrates for the first time the feasibility of producing PHA from chestnut wood residues, including industrial detannized byproducts, without nutrient supplementation. These findings highlight the potential of tannin-industry waste streams as alternative feedstocks for biopolymer production, while indicating that optimization of hydrolysis conditions, detoxification efficiency, and fermentation strategy is required to improve process performance. Full article

A novel citric acid-assisted in situ reduction method has been developed for the synthesis of bimetallic AuPd alloy nanoparticles supported on amine–phosphate-functionalized carbon nanotubes (AuPd/NH₂-P-CNTs). In this strategy, formic acid acts not only as the reducing agent for reducing metal precursors, but also as the hydrogen source for the subsequent catalytic dehydrogenation. The introduction of citric acid significantly accelerates the reduction kinetics and promotes the uniform formation of ultrafine AuPd nanoparticles (∼1.8 nm). As a result, the optimized Au_0.5Pd_0.5/NH₂-P-CNTs exhibit an extraordinary catalytic activity and 100% H₂ selectivity during hydrogen generation from FA with sodium formate as an additive, affording a remarkable initial turnover frequency of 5663.94 mol H₂ mol Pd⁻¹ h⁻¹ at 303 K. The experimental results reveal that the -NH₂ and -P functional groups on the support are crucial for stabilizing and uniformly dispersing the alloy nanoparticles. Furthermore, the enhanced reaction rate can be attributed to the strong metal–support interaction established between AuPd nanoparticles and -NH₂-P-CNT supports. This work provides a new perspective on the design of highly efficient Pd-based catalysts for hydrogen production from formic acid. Full article

4-(2-Aminophenyl)-4-oxobutyronitriles in the presence of formic acid (HCOOH) and p-toluenesulfonic acid (TsOH) undergo an unusual rearrangement providing access to a range of 3-(quinazolin-4-yl)propionic acids that have been poorly represented in the literature, with only a few isolated examples known to date. The reaction demonstrates a new route to the quinazoline core through transfer of the nitrile group nitrogen, mediated through the formation of a pyrrolidine cycle. The availability of 4-oxobutyronitrile precursors—2′-aminochacones—provides high variability of substituents in the required positions of product. The transformation is general and can be extended to the preparation of 2-substituted 3-(quinazolin-4-yl)propionic acids through preliminary acylation or to the synthesis of 4-(quinazolin-4-yl)butyric acids. Full article

This study proposes a sustainable, integrated biorefinery approach to valorize mussel shell waste into high-value products, including chitin, chitosan, and calcium formate. Formic acid was employed as an effective demineralizing agent, enabling not only efficient mineral removal but also the direct conversion of the demineralization effluent into value-added calcium formate. The sequential extraction processes, demineralization, deproteinization, and decolorization, successfully yielded purified chitin (PCH), which was subsequently deacetylated to produce chitosan (CTS) with a degree of deacetylation of 85% and a molecular weight of 75 kDa. The physicochemical properties of all products were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR and XRD analyses confirmed the successful extraction of chitin and chitosan, demonstrating the feasibility of mussel shells as an alternative biopolymer source. In parallel, calcium formate (CCF) was obtained from the demineralization effluent with a yield of 94.19%, and its formation was verified by FTIR and XRD. Elemental analysis by XRF exhibited 98.3% CaO with minimal non-toxic impurities. The TGA/DTG profiles of CCF exhibited a well-defined two-step thermal decomposition, confirming its anhydrous form. Overall, this environmentally benign process enables the simultaneous production of multiple value-added products while significantly improving resource utilization and reducing waste generation. The proposed integrated biorefinery model offers a promising, economically viable pathway for marine biomass valorization, aligned with the Bio-Circular-Green (BCG) economy concept. Full article

Calcium formate (Ca(HCOO)₂) is an important industrial chemical widely used in construction, feed additives, and various chemical processes. In this work, calcium formate was synthesized from cockle shell waste and concentrated formic acid (50%, 60%, and 70% w/w) by a simple, rapid, low-cost, and environmentally friendly process, denoted as CF50, CF60, and CF70, respectively. The chemical and physical properties of as-synthesized calcium formate using cockle shells as a renewable calcium source were investigated by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray fluorescence (XRF), Thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) techniques. The FTIR and XRD results revealed that the samples prepared using 50% and 60% formic acid produced well-crystallized α-calcium formate. In contrast, the reaction using 70% formic acid generated a strongly exothermic reaction, which hindered the complete conversion of calcium carbonate and resulted in the presence of residual CaCO₃ in the final product. Similarly, the SEM images of the CF50 and CF60 samples show the slick surface of orthorhombic crystals of calcium formate; on the other hand, the SEM image of CF70 shows some small particles of aragonite on the surface of the calcium formate crystals. The 60% formic acid provided the optimal synthesis condition, yielding pure calcium formate with the shortest synthesis time. Overall, the proposed approach provides a simple, rapid, and cost-effective route for producing calcium formate from shell waste. Furthermore, the utilization of cockle shell waste as a renewable calcium source contributes to waste valorization, reduces environmental impacts associated with shell disposal, and minimizes dependence on mined limestone resources, supporting sustainable resource utilization within a circular economy. Full article

The electrochemical CO₂ reduction reaction (CO₂RR) offers a sustainable route for converting greenhouse gases into high-value fuels; however, its efficiency has long been constrained by the thermodynamic stability of CO₂ molecules and the competing hydrogen evolution reaction. Using density functional theory (DFT) calculations, this work systematically investigates the catalytic performance of Ni₅ and alloy Ni₄Cu clusters anchored on divacancy graphene (DVG) for CO₂RR. The results demonstrate that the introduction of Cu atoms significantly enhances the interfacial binding energy between the cluster and the support (shifting from −6.2 eV to −7.5 eV). Charge density difference analysis combined with Bader charge analysis further reveals that interfacial charge transfer and the formation of Ni–C bonds serve as the electronic origin of this improved stability. Free energy calculations show that, compared to Ni₅/DVG, Ni₄Cu/DVG substantially reduces the energy barrier of the rate-determining step for formic acid (HCOOH) formation from 1.18 eV to 0.26 eV, thereby significantly optimizing the reaction kinetics. Crystal orbital Hamilton population (COHP) analysis demonstrates that Cu doping modulates metal–oxygen bond strength in the key *OCHO intermediate (ICOHP: Ni-O bonds at −0.697 eV/−0.976 eV vs. Cu-O bonds at −0.408 eV/−0.492 eV), optimizing the adsorption–desorption balance and steering selectivity toward HCOOH. This work elucidates the atomic-scale electronic and bonding mechanisms underlying Ni–Cu synergistic effects, providing theoretical guidance for designing efficient non-noble metal CO₂RR electrocatalysts. Full article

Polyfarnesene, a bio-based polymer, was epoxidized in situ using performic acid to investigate oxirane ring formation, stability, and the role of its bottlebrush architecture in the kinetics. The reaction reached a maximum epoxidation degree of ~20% after 6 h but underwent side reactions, producing hydroxyl and formic ester groups. FTIR and ¹H NMR revealed that ring opening began within the first hour, whereas residual unsaturated bonds persisted after prolonged reaction, owing to steric shielding by the polymer’s long C11–C13 side chains. Unlike smaller polydiene homologues, polyfarnesene exhibited slower ring-opening kinetics, retaining approximately 10% of oxirane groups after 20 h. GPC showed minimal molecular weight changes but an increase in polydispersity, confirming structural rearrangements without chain scission or crosslinking. DSC demonstrated that oxirane incorporation increased the T_g; however, side reactions reduced this effect by limiting chain mobility. These findings establish that the spatial constraints imposed by the bottlebrush architecture of polyfarnesene govern the reaction kinetics, restricting epoxidation efficiency and favoring esterification pathways. This interplay provides a basis for designing bio-based polymers with tunable thermal properties. Controlling the reaction environment to suppress side reactions is key to producing high-T_g epoxidized derivatives suitable for rubber technologies and sustainable materials. Full article

Metal–organic frameworks (MOFs) are unique microporous materials being explored for a wide range of applications. Their porosity and high surface areas can readily be exploited for guest–host interactions, separations, and photochemical catalysis, but many suffer from poor charge separation and fast electron–hole recombination. Introducing structural defects, such as missing linkers or metal nodes, can create unsaturated metal sites and alter band structure, conductivity, and light absorption, improving photocatalytic performance. UiO-66-NH₂ and MIL-125-NH₂ are water-stable, visible-light-absorbing MOFs well suited for photocatalytic degradation of organic dyes. In this work, the influence of defect engineering on photocatalytic properties of MOFs was investigated using formic and acetic acid modulators with UiO-66-NH₂ and variable temperature with MIL-125-NH₂ during synthesis. The resulting materials were characterized by XRD, FTIR and SEM/EDS. Defect states were tracked using N₂ adsorption/BET analysis and UV–Vis spectroscopy. Photocatalytic activity was evaluated by monitoring Rhodamine B (RhB) degradation in aqueous solution under simulated solar irradiation. It was found that increased temperature beyond 120 °C during synthesis promotes mesopore formation and decreases the bandgap in MIL-125-NH₂, resulting in a more photoactive material. Defective MIL-125-NH₂ synthesized at 150 °C showed the most defects and proved to be the best photocatalyst investigated in this study. Formic acid modulation in UiO-66-NH₂ generated smaller crystallites that slightly increased the bandgap; however, the surface area decreased proportionally with the amount of formic acid used. The decreased surface area and observed enhancement in photocatalytic degradation of RhB suggest that formic acid introduces defects into the UiO-66-NH₂ framework that enhance photocatalytic properties. UiO-66-NH₂ treated with acetic acid resulted in larger crystals, increased bandgaps, and increased surface areas, suggesting that acetic acid simply modulates growth rather than imparting defects to the framework. Full article

This study investigates the impact of ethanol as a co-solvent in hydrothermal carbonization (HTC) of sewage sludge, a process referred to here as ethanothermal or solvothermal carbonization. Experiments were conducted at 180 °C, 200 °C, 220 °C, and 240 °C, comparing two sets of conditions: one using water (S/W) and the other using ethanol (S/E) as the reaction medium. The focus was placed on the composition of the aqueous phase, particularly the formation of volatile fatty acids (VFAs). Ethanol-assisted experiments consistently produced more alkaline process water (pH 7.6–8.2) compared to water-based runs. COD values in S/W samples ranged from 9358 mg/L to 19,756 mg/L, indicating significant organic loading. Hydrochar derived from the ethanol experiments exhibited higher energy content, with a peak high heating value (HHV) of 21.9 MJ/kg at 240 °C, compared to 19.9 MJ/kg in S/W samples. VFA concentrations were also enhanced under ethanothermal conditions, especially at lower temperatures: formic acid (30.4–34.8 mg/L), acetic acid (8.7–9.6 mg/L), and propionic acid (10.8–14.6 mg/L). These results demonstrate ethanol’s potential to enhance both the yield and quality of liquid and solid products in HTC of sewage sludge. Full article

For Co-N-C materials prepared under high-temperature calcination conditions, the formation of Co nanoparticles occurs when the metal loading exceeds 2%. Typically, CoNx is regarded as the primary active site of the catalyst, while Co nanoparticles are considered to possess limited catalytic activity. Consequently, within Co-N-C materials, Co nanoparticles are often likened to ‘ballast stone’ in a catalyst. In the model reaction of formic acid dehydrogenation, we incorporated boron into the precursor, thereby enhancing the electronic metal-support interactions (EMSI) between Co nanoparticles and carbon carriers. Consequently, this modification resulted in a catalytic performance of Co nanoparticles that was comparable to that of Co single-atom catalysts (SACs). Full article

Catalytic transfer hydrogenation (CTH) provides a practical and sustainable approach for reducing unsaturated compounds, serving as an alternative to high-pressure H₂ in laboratory and fine chemical contexts. This broad reaction class includes asymmetric transfer hydrogenation (ATH), a key strategy in enantioselective synthesis due to its operational simplicity, high stereocontrol, and compatibility with sensitive functional groups. A central variable governing CTH efficiency is the role of bases, which may function as essential activators, co-hydrogen donors, or be entirely absent depending on the catalytic system. This review provides a comparison of base-assisted, base-free, and base-as-co-hydrogen-donor CTH methodologies across diverse metal catalysts and substrates. We highlight how bases such as triethylamine, K₂CO₃, and NaOH facilitate catalyst activation, modulate hydride formation, and tune reactivity and selectivity. The dual function of bases in formic-acid-driven systems is examined alongside synergistic effects observed with mixed-base additives. In contrast, base-free CTH platforms demonstrate how tailored ligand frameworks, metal-ligand cooperativity, and engineered surface basicity can eliminate the need for external additives while maintaining high activity. Through mechanistic analysis and cross-system comparison, this review identifies the key structural, electronic, and environmental factors that differentiate base-assisted from base-free pathways. Emerging trends—including greener hydrogen donors, advanced catalyst architectures, and additive-minimized protocols—are discussed to guide future development of sustainable CTH processes. Full article

Triple-cation perovskite solar cells, such as Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃ (hereinafter referred to as CsFAMA) have high efficiency (>26%), but their stability is limited by phase segregation and defects at grain boundaries. In this work, the effect of formic acid (HCOOH) on suppressing the degradation of perovskite films is investigated. It is shown that the addition of HCOOH to the precursor solution reduces the size of colloidal particles by 90%, which contributes to the formation of highly homogeneous films with a photoluminescence intensity deviation of ≤3%. Structural analysis and dynamic light scattering measurements confirmed that HCOOH suppresses iodide oxidation and cation deprotonation, reducing the defect density. Aging tests (ISOS-D) demonstrated an increase in the T80 lifetime (time to 80% efficiency decline) from 158 to 320 days for the modified cells under ambient conditions at room temperature and 40% relative humidity. The obtained results indicate a key role of HCOOH in stabilizing CsFAMA perovskite by controlling colloidal dynamics and defect passivation, which opens up prospects for the creation of commercially viable PSCs. Full article

Silk proteins are versatile biopolymers well-suited to act as foundational components of a wide range of biomaterials. Rapidly gelling, self-assembling systems are especially valuable for drug delivery and biomedical applications. In this study, we present a way to induce the solid coaggregation of silk fibroin (SF) by adding the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) into an SF solution prepared in formic acid (FA). SF films prepared by dissolving silk in CaCl₂–FA and subsequently rinsing in water to remove CaCl₂ were re-solubilized in FA with different content of SDBS. It was found that SF aggregation time is strongly modulated by the presence of SDBS. At increasing surfactant content, hydrophobic interactions between the SF chains and SDBS promote the formation of spherical coaggregates, whose size increases with surfactant concentration. FTIR analysis reveals that this process is accompanied by the formation of β-sheet structures, likely driven by hydrophobic interactions. This spontaneous liquid-to-solid phase transition promotes the formation of mechanically robust SF films with tunable electrical properties. Full article

Due to high thermodynamic stability, the direct generation of formic acid by CO₂ hydrogenation is not easy to achieve experimentally. However, when Nakahara and coworkers studied the equilibrium of formic acid reversibly decomposing into CO₂ and H₂, they found that using imidazolium formate ionic liquid as an additive could shift the reaction equilibrium to the formic acid side. Subsequently, imidazolium acetate ionic liquid and imidazolium bicarbonate ionic liquid have also been experimentally proven to be able to be used for CO₂ hydrogenation to directly produce formic acid. In order to investigate the mechanism of action of ionic liquids in the process of CO₂ catalyzed hydrogenation to formic acid, we performed DFT calculations. The results showed that, after the hydrogenation of CO₂ to formic acid, the ionic liquids and formic acid molecules form adducts through hydrogen bonding, and then stabilize the product formic acid. The further use of methyl to replace H at the position of the cation R3 of the ionic liquids can improve the ability of the ionic liquids to stabilize formic acid, which also supports the experimental work of Nakahara and coworkers. In addition, among the three ionic liquids, the imidazolium acetate ionic liquid had the best stabilizing effect on formic acid, and the second best is the imidazolium formate ionic liquid, while the imidazolium bicarbonate ionic liquid has a relatively weak stabilizing ability. Full article