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Reducing the ever-growing level of CO2 in the atmosphere is critical for the sustainable development of human society in the context of global warming. Integration of the capture and upgrading of CO2 is, therefore, highly desirable since each process step is costly, both energetically and economically. Here, we report a CO2 direct air capture (DAC) and fixation process that produces methane. Low concentrations of CO2 (∼400 ppm) in the air are captured by an aqueous solution of sodium hydroxide to form carbonate. The carbonate is subsequently hydrogenated to methane, which is easily separated from the reaction system, catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9% among gas-phase products. The concurrent regenerated hydroxide, in turn, increases the alkalinity of the aqueous solution for further CO2 capture, thereby enabling this one-of-its-kind continuous CO2 capture and methanation process. Engineering simulations demonstrate the energy feasibility of this CO2 DAC and methanation process, highlighting its promise for potential large-scale applications.

The hydrogenation of nitriles to amines, as an atom-economical synthetic route, has attracted wide attention in industrial production. Despite that some catalysts for nitrile hydrogenation have been investigated in recent years, achieving high activity and selectivity in this process remains a major challenge. Here, we fabricated an atomically dispersed Rh catalyst anchored on defect-rich nanodiamond-graphene (ND@G) via a deposition–precipitation strategy (Rh1/ND@G), which showed the highest activity (TOF = 2592 h–1) in the hydrogenation of benzonitrile reaction among all the known catalysts under mild reaction conditions (333 K, 0.6 MPa H2), and delivered high selectivity (>99%) toward secondary amines. Significantly, we prepared the Rh-cluster catalyst (Rhn/ND@G) and a series of atomically dispersed M1 catalysts (M = Rh, Ru, Pd, Ir, and Pt) to understand the size effect and metal-dependent effect in the hydrogenation of benzonitrile. Experimental and theoretical investigations revealed that the Rh1/ND@G catalyst has higher selectivity toward dibenzylamine than Rhn/ND@G, as it is less likely to form benzylamine on the Rh1 active sites. Meanwhile, the difference of adsorption energies (as a catalyst descriptor) between benzylideneimine and benzonitrile was used to understand the activity of benzonitrile hydrogenation influenced by the metal-dependent effect of M1 catalysts. Modulating the size and metal-dependent effects could lead to high catalytic performance, paving the way to design efficient nitrile hydrogenation catalysts.

A simple and efficient strategy was developed for the synthesis of Pd single-atom catalysts (Pd-SA/G) by nitric acid vapor-assisted redispersion. The as-prepared Pd-SA/G displayed robust catalytic performance in the selective hydrogenation reaction of benzaldehyde. This work paves a new way for the design of supported Pd single-atom catalysts.

Selective hydrogenation of alkynes to alkenes plays a crucial role in the synthesis of fine chemicals. However, how to achieve high selectivity and effective separation of the catalyst and substrate while obtaining high activity is the key for this reaction. In this work, a Pd single-atom catalyst is anchored to the shell of magnetic core–shell particles that consist of a Ni-nanoparticles core and a graphene sheets shell (Ni@G) for semi-hydrogenation of phenylacetylene, delivering 93% selectivity to styrene at full conversion with a robust turnover frequency of 7074 h−1 under mild reaction conditions (303 K, 2 bar H2). Moreover, the catalyst can be recovered promptly from the liquid phase due to its magnetic separability, which makes it present good stability for enduring five cycles. Experimental and theoretical investigations reveal that H2 and substrates are activated by atomically dispersed Pd atoms and Ni@G hybrid support, respectively. The hydrogenation reaction occurs on the surface of Ni@G via hydrogen spillover from the metal to the support. Such a strategy opens an avenue for designing highly active, selective, and magnetically recyclable catalysts for selective hydrogenation in liquid reaction systems. © 2022 Wiley-VCH GmbH.

Dry reforming of methane (DRM) has provided an effective avenue to convert two greenhouse gases, CH4 and CO2, into syngas. Here, we design a DRM photocatalyst Rh/CexWO3 that invokes both photothermal and photoelectric processes, which overcomes the thermodynamic limitation of DRM under conventional conditions. In contrast to plasmonic or UV-response photocatalysts, our photocatalyst produces a superior light-to-chemical energy efficiency (LTCEE) of 4.65 % with a moderate light intensity. We propose that a light-induced metal-to-metal charge transfer plays a crucial role in the DRM reaction, which induces a redox looping between Ce to W species to lower the activation energy. Quantum mechanical studies reveal that a high oxygen mobility of CexWO3, accompanied with the formation of oxo-bridge species, results in a substantial elimination of deposited C species during the reaction. Our catalyst design strategy could offer a promising energy-efficient industrial process for DRM.

The atomically dispersed metal catalyst or single-atom catalyst (SAC) with the utmost metal utilization efficiency shows excellent selectivity toward ethylene compared to the metal nanoparticles catalyst in the acetylene semi-hydrogenation reaction. However, these catalysts normally work at relatively high temperatures. Achieving low-temperature reactivity while preserving high selectivity remains a challenge. To improve the intrinsic reactivity of SACs, rationally tailoring the coordination environments of the first metal atom by coordinating it with a second neighboring metal atom affords an opportunity. Here, we report the fabrication of a dual-atom catalyst (DAC) that features a bonded Pd1-Cu1atomic pair anchoring on nanodiamond graphene (ND@G). Compared to the single-atom Pd or Cu catalyst, it exhibits increased reactivity at a lower temperature, with 100% acetylene conversion and 92% ethylene selectivity at 110 °C. This work provides a strategy for designing DACs for low-temperature hydrogenation by manipulating the coordination environment of catalytic sites at the atomic level. © 2022 American Chemical Society. All rights reserved.

Exploring antibacterial nanomaterials with excellent catalytic antibacterial properties has always been a hot research topic. However, the construction of nanomaterials with robust antibacterial activity at the atomic level remains a great challenge. Here a fully-exposed Pd cluster atomically-dispersed on nanodiamond-graphene (Pd-n/ND@G) with excellent catalytic antibacterial properties is reported. The fully-exposed Pd cluster nanozyme provides atomically-dispersed Pd cluster sites that facilitate the activation of oxygen. Notably, the oxidase-like catalytic performance of the fully-exposed Pd cluster nanozyme is much higher than that of Pd single-atom oxidase mimic, Pd nanoparticles oxidase mimic and even the previously reported palladium-based oxidase mimics. Under the density functional theory (DFT) calculations, the Pd cluster sites can efficiently catalyze the decomposition of oxygen to generate reactive oxygen species, resulting in strong antibacterial properties. This research provides a valuable insight to the design of novel oxidase mimic and antibacterial nanomaterial.