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Integrating air capture and conversion of CO 2 is key to realizing energy sustainability. However, current integration approaches require high temperature and pressure, making them energy intensive. Here, we demonstrate a nanoparticle (NP) catalysis approach for the hydrogenation of alkyl carbonate, an intermediate obtained from the CO 2 capture process, to formate, achieving one-pot air capture and conversion of CO 2 under ambient conditions. The capture is realized in an ethylene glycol (EG) solution of KOH (EG-KOH) at room temperature, where CO 2 is selectively converted into HO-CH 2 CH 2 -O-COOK (∼100% conversion). This carbonate is then hydrogenated using ammonia borane (under ambient pressure and at 50 °C) to formate (HCOOK) (>90% yield) in the presence of a stable Pd NP catalyst with EG being regenerated. Atomistic simulations suggest that the CO 2 absorption process in the EG-KOH solution is energetically stable, and the catalyst surface provides the reaction site to break the C-O bond in the -O-COOK structure, enabling the hydrogenation of the alkyl carbonate to formate and the regeneration of EG. Our study provides a promising NP-catalysis approach for air capture and conversion of CO 2 into value-added chemicals/fuels under ambient conditions.

Given the continuous and excessive CO 2 emission into the atmosphere from anthropomorphic activities, there is now a growing demand for negative carbon emission technologies, which requires efficient capture and conversion of CO 2 to value-added chemicals. This review highlights recent advances in CO 2 capture and conversion chemistry and processes. It first summarizes various adsorbent materials that have been developed for CO 2 capture, including hydroxide-, amine-, and metal organic framework-based adsorbents. It then reviews recent efforts devoted to two types of CO 2 conversion reaction: thermochemical CO 2 hydrogenation and electrochemical CO 2 reduction. While thermal hydrogenation reactions are often accomplished in the presence of H 2 , electrochemical reactions are realized by direct use of electricity that can be renewably generated from solar and wind power. The key to the success of these reactions is to develop efficient catalysts and to rationally engineer the catalyst-electrolyte interfaces. The review further covers recent studies in integrating CO 2 capture and conversion processes so that energy efficiency for the overall CO 2 capture and conversion can be optimized. Lastly, the review briefs some new approaches and future directions of coupling direct air capture and CO 2 conversion technologies as solutions to negative carbon emission and energy sustainability.

We report the synthesis of Cu 2 O nanoparticles (NPs) by controlled oxidation of Cu NPs and the study of these NPs as a robust catalyst for ammonia borane dehydrogenation, nitroarene hydrogenation, and amine/aldehyde condensation into Schiff-base compounds. Upon investigation of the size-dependent catalysis for ammonia borane dehydrogenation and nitroarene hydrogenation using 8-18 nm Cu 2 O NPs, we found 13 nm Cu 2 O NPs to be especially active with quantitative conversion of nitro groups to amines. The 13 nm Cu 2 O NPs also efficiently catalyze tandem reactions of ammonia borane, diisopropoxy-dinitrobenzene, and terephthalaldehyde, leading to a controlled polymerization and the facile synthesis of polybenzoxazole (PBO). The highly pure PBO ( M w = 19 kDa) shows much enhanced chemical stability than the commercial PBO against hydrolysis in boiling water or simulated seawater, demonstrating a great potential of using noble metal-free catalysts for green chemistry synthesis of PBO as a robust lightweight structural material for thermally and mechanically demanding applications.

We report a simple strategy to synthesize anisotropic SmCo5 nanoplates. The strategy involves the pre-synthesis of 125 × 12 nm Sm(OH)3 nanorods and 10 nm Co nanoparticles followed by the self-assembly of these nanorods and nanoparticles into Sm(OH)3-Co nanocomposites. Once embedded in a CaO matrix, the nanocomposite is subjected to high temperature (850 °C) annealing in the presence of Ca, leading to the formation of 125 × 10 nm SmCo5 nanoplates, which are dispersible in ethanol, allowing the alignment in epoxy resin under a 20 kOe magnetic field. The aligned SmCo5 nanoplates show a square hysteresis behavior with room temperature coercivity reaching 30.1 kOe, which is among the highest values ever reported for SmCo5 made from chemical methods. This work provides a new approach to high-performance anisotropic SmCo5 for permanent magnetic applications.

We report a facile synthesis of Au-Fe heterodimer nanoparticles (NPs) with tunable Au/Fe sizes and their sequential oxidations to Au-Fe 3 O 4 heterostructured NPs with controllable morphologies. The size of Au in Au-Fe heterodimer NPs was tuned to be 4, 7 and 10 nm, while the Fe crystal structure was maintained as single-crystal bcc. Further oxidation of the as-synthesized Au-Fe NPs led to the formation of Au-hollow Fe 3 O 4 yolk-shell, Au-hollow Fe 3 O 4 heterodimer NPs and Au-porous hollow Fe 3 O 4 yolk-shell NPs, depending on the size of the Au-Fe NPs and the oxidation conditions used. Our study has provided not only a variety of bifunctional NPs with tunable surface plasmon absorption and magnetic properties, but also a new general approach to design and synthesize multicomponent NPs with multiple heterostructures.

Using reduced graphene oxide (rGO) as a template and high temperature sol-gel chemistry, we have prepared LaFeO3 nanoparticles (NPs). The 15 nm LaFeO3 NPs have a bandgap of 1.86 eV and the LaFeO3-rGO can function as an efficient catalyst for degradation of methylene blue (MB) or Rhodamine B (RhB) under visible-light irradiation with the electron transfer from the dye to hole dominating the oxidation process. The reported synthesis offers a general approach to perovskite-type NPs for efficient photocatalytic applications.