The current environmental consciousness of the world\'s population encourages researchers to work on new materials that are environmentally benign and able to display the appropriate features for the needed application. To develop high-performing, inexpensive eco-materials, scientists have frequently turned to nature, attempting to mimic its processes\' excellent performance at a reasonable price. In this regard, we decided to focus on alginic acid (AA), a polysaccharide widely found in brown algae, and kojic acid (KA), a chelating agent fungi produces. This study proposes rapidly synthesizing a sustainable, biocompatible material (AK) based on AA and KA, employing chlorokojic acid (CKA). The material has a dual function: antibacterial activity on both Gram-positive and Gram-negative bacteria, without any cytotoxic action on human cells in vitro, and catalytic ability to convert CO2 into cyclic carbonates at atmospheric pressure, without solvents, with high yields, and without the use of metals. Furthermore, the material\'s insolubility in organic solvents allows it to be easily separated from the reaction product and reused for other catalytic cycles. Both applications have a key role in the medical and environmental fields, combating the outbreak of infections and providing an innovative methodology to fix the CO2 on specific substrates.

We introduced a new class of gas diffusion electrodes (GDEs) with adjustable pore morphology. We fabricated intrinsically conductive polymer-composite membranes containing carbon filler, enabling a pore structure variation through film casting cum phase separation protocols. We further selectively functionalized specific pore regions of the membranes with Cu by a NaBH4-facilitated coating strategy. The as-obtained GDEs can facilitate the electrochemical CO2 reduction reaction (CO2RR) at Cu active sites that are presented inside a defined and electrically conductive pore system. When employing them as free-standing cathodes in a CO2 flow electrolyzer, we achieved >70% Faradaic efficiencies for CO2RR products at up to 200 mA/cm2. We further demonstrated that deposition of a dense Cu layer on top of the membrane leads to obstruction of the underlying pore openings, inhibiting an excessive wetting of the pore pathways that transport gaseous CO2. However, the presentation of Cu inside the pore system of our novel membrane electrodes increased the C2H4/CO selectivity by a factor of up to 3 compared to Cu presented in the dense layer on top of the membrane. Additionally, we found that gaseous CO2 could still access Cu in macropores after wetting with electrolyte, while CO2RR was completely suppressed in wetted nm-scale pores.

The rapid pace of industrialization has led to a multitude of detrimental environmental consequences, including water pollution and global warming. Consequently, there is an urgent need to devise appropriate materials to address these challenges. Ionic porous organic polymers (iPOPs) have emerged as promising materials for oxoanion sequestration and non-redox CO2 fixation. Notably, iPOPs offer hydrothermal stability, structural tunability, a charged framework, and readily available nucleophilic counteranions. This review explores the significance of pores and charged functionalities alongside design strategies outlined in existing literature, mainly focusing on the incorporation of pyridinium and imidazolium units into nitrogen-rich iPOPs for oxoanion sequestration and non-redox CO2 fixation. The present review also addresses the current challenges and future prospects, delineating the design and development of innovative iPOPs for water treatment and heterogeneous catalysis.

Iron porphyrins are known to provide CH4 as an eight-electron reduction product of CO2 in a photochemical reaction. However, there are still some aspects of the reaction mechanism that remain unclear. In this study, we synthesized iron porphyrin dimers and carried out the photochemical CO2 reduction reactions in N,N-dimethylacetamide (DMA) containing a photosensitizer in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. We found that, despite a low catalytic turnover number, CH4 was produced only when these porphyrins were facing each other. The close proximity of the cyclic dimers, distinguishing them from a linear Fe porphyrin dimer and monomers, induced multi-electron CO2 reduction, emphasizing the unique role of their structural arrangement in CH4 formation.

Catalytic transformation of CO2 into value-added chemical products can provide an appropriate solution for the raising environmental issues. To date, various metal-organic frameworks (MOFs) with transition metal ions have been explored for CO2 capture and conversion, but alkaline earth metal-based MOFs are comparatively less studied. Metal ions like Sr(II) having relatively large radius give rise to a high coordination number resulting in higher stability of the MOFs. Moreover, the introduction of N-rich functional group in organic linker like -NH2, -CONH- and triazole into MOF backbone enhance their CO2 capture and conversion efficiency. Herein, the effect of amine group on the catalytic efficiency of MOFs for CO2 cycloaddition with epoxides under solvent free and ambient conditions are presented. The di-carboxylates, such as 5-aminoisophthalate (AmIP) and 5-bromoisophthalate (BrIP) were utilized to synthesize Sr(II) based MOFs. The Zn(II) MOF was synthesized using tetra-carboxylate containing amide spacer (OAT) and 4-amino-4H-1,2,4-triazole (AMT). All three MOFs exhibited porous networks with guest available volume ranging from 15 to 58 %. The catalytic efficiency of the MOFs towards carbon dioxide fixation reaction was explored. The catalytic performances revealed that the presence of amine group in the channels enhances the catalytic efficiency of the MOFs.

[This corrects the article DOI: 10.3389/fmicb.2022.872708.].

Electrochemical reduction of CO2 and nitrate offers a promising avenue to produce valuable chemicals through the using of greenhouse gas and nitrogen-containing wastewater. However, the generally proposed reaction pathway of concurrent CO2 and nitrate reduction for urea synthesis requires the catalysts to be both efficient in both CO2 and nitrate reduction, thus narrowing the selection range of suitable catalysts. Herein, we demonstrate a distinct mechanism in urea synthesis, a tandem NO3 - and CO2 reduction, in which the surface amino species generated by nitrate reduction play the role to capture free CO2 and subsequent initiate its activation. When using the TiO2 electrocatalyst derived from MIL-125-NH2, it intrinsically exhibits low activity in aqueous CO2 reduction, however, in the presence of both nitrate and CO2, this catalyst achieves an excellent urea yield rate of 43.37 mmol ⋅ g-1 ⋅ h-1 and a Faradaic efficiency of 48.88 % at -0.9 V vs. RHE in a flow cell. Even at a low CO2 level of 15 %, the Faradaic efficiency of urea synthesis remains robust at 42.33 %. The tandem reduction procedure was further confirmed by in situ spectroscopies and theoretical calculations. This research provides new insights into the selection and design of electrocatalysts for urea synthesis.

Perovskite CsPbBr3 quantum dot shows great potential in artificial photosynthesis, attributed to its outstanding optoelectronic properties. Nevertheless, its photocatalytic activity is hindered by insufficient catalytic active sites and severe charge recombination. In this work, a CsPbBr3@Ag-C3N4 ternary heterojunction photocatalyst is designed and synthesized for high-efficiency CO2 reduction. The CsPbBr3 quantum dots and Ag nanoparticles are chemically anchored on the surface of g-C3N4 sheets, forming an electron transfer tunnel from CsPbBr3 quantum dots to Ag nanoparticles via g-C3N4 sheets. The resulting CsPbBr3@Ag-C3N4 ternary photocatalyst, with spatial separation of photogenerated carriers, achieves a remarkable conversion rate of 19.49 μmol·g-1·h-1 with almost 100 % CO selectivity, a 3.13-fold enhancement in photocatalytic activity as compared to CsPbBr3 quantum dots. Density functional theory calculations reveal the rapid CO2 adsorption/activation and the decreased free energy (0.66 eV) of *COOH formation at the interface of Ag nanoparticles and g-C3N4 in contrast to the g-C3N4, leading to the excellent photocatalytic activity, while the thermodynamically favored CO desorption contributes to the high CO selectivity. This work presents an innovative strategy of constructing perovskite-based photocatalyst by modulating catalyst structure and offers profound insights for efficient CO2 conversion.

The recovery of spent lithium-ion batteries by traditional acid leaching is limited by serious pollution, complicated technology, and the low purity of Li2CO3. To address the problems of the traditional acid leaching process and increasing demand for decarbonization, a technique for the selective carbonation leaching of Li and the recovery of battery-grade Li2CO3 by a simple concentration precipitation process without acids or bases was developed. The coupling of CO2 and reducing agents could effectively promote the precipitation of MCO3 (M=Ni/Co/Mn) and the selective leaching of Li by decreasing the reducing capability needed for transition metals and decreasing the pH of the solution. The optimal selective leaching process of Li was obtained under 1 MPa CO2 with 20 g/L Na2S2O3 at an L/S ratio of 30 mL/g for 1.5 h. FT-IR, XRD, ICP-MS and other methods were used to reveal the multiphase interfacial reaction mechanism of the carbonation reduction of layered cathode materials, which indicated that the reducing agent Na2S2O3 could promote lattice distortion of the cathode materials and effective separation of Li. In summary, a green and economical method for the selective recovery of battery-grade Li2CO3 using a one-step method of CO2 carbonation recovery in a near-neutral environment was proposed.

Mismatched reaction kinetics of CO2 reduction and H2O oxidation is the main obstacle limiting the overall photocatalytic CO2 conversion. Here, a molten salt strategy is used to construct tubular triazine-based carbon nitride (TCN) with more adsorption sites and stronger activation capability. Ni(OH)2 nanosheets are then grown over the TCN to trigger a proton-coupled electron transfer for a stoichiometric overall photocatalytic CO2 conversion via \"3CO2 + 2H2O = CH4 + 2CO + 3O2.\" TCN reduces the energy barrier of H2O dissociation to promote H2O oxidation to O2 and supply sufficient protons to Ni(OH)2, whereby the CO2 conversion is accelerated due to the enhanced proton-coupled electron transfer process enabled by the sufficient proton supply from TCN. This work highlights the importance of matching the reaction kinetics of CO2 reduction and H2O oxidation by proton-coupled electron transfer on stoichiometric overall photocatalytic CO2 conversion.