Cobalt Imidazolate Metal–Organic Frameworks Photosplit CO2 under Mild Reaction Conditions

Metal–organic frameworks (MOFs) have shown great promise for CO₂ capture and storage. However, the operation of chemical redox functions of framework substances and organic CO₂‐trapping entities which are spatially linked together to catalyze CO₂ conversion has had much less attention. Reported herein is a cobalt‐containing zeolitic imidazolate framework (Co‐ZIF‐9) which serves as a robust MOF cocatalyst to reduce CO₂ by cooperating with a ruthenium‐based photosensitizer. The catalytic turnover number of Co‐ZIF‐9 was about 450 within 2.5 hours under mild reaction conditions, while still keeping its original reactivity during prolonged operation.     

空心NiCo2S4纳米球助催化剂担载ZnIn2S4纳米片用于可见光催化制氢

纳米片与空心球上之间的合理界面调控是开发高效太阳能制氢光催化剂的潜在策略。在各类光催化材料中,金属硫化物由于具有相对较窄的带隙和优越的可见光响应能力而被广泛研究。ZnIn₂S₄是一种层状的三元过渡金属半导体光催化剂,其带隙可控(约2.4 eV)。在众多金属硫化物光催化剂中,ZnIn₂S₄引起了广泛兴趣。然而,单纯的ZnIn₂S₄光催化活性仍然相对较差,主要是因为光生载流子的复合率较高、迁移速率较慢。在半导体光催化剂上负载助催化剂是提升光催化剂性能的一种有效方法,因为它不仅可以加速光生电子和空穴的分离,而且还可以降低质子还原反应的活化能。作为一种三元过渡金属硫化物,NiCo₂S₄表现出较高的导电性、较低的电负性、丰富的氧化还原特性以及优越的电催化活性。这些特性表明,NiCo₂S₄可以作为光催化制氢的助催化剂,以加速电荷分离和转移。此外,NiCo₂S₄和ZnIn₂S₄都属于三元尖晶石的晶体结构,这可能有助于构建具有紧密界面接触的NiCo₂S₄/ZnIn₂S₄复合物,从而提高光催化性能。本文中,将超薄ZnIn₂S₄纳米片原位生长到非贵金属助催化剂NiCo₂S₄空心球上,形成具有强耦合界面和可见光吸收的NiCo₂S₄@ZnIn₂S₄分级空心异质结构光催化剂。最优NiCo₂S₄@ZnIn₂S₄复合样品(NiCo₂S₄含量：ca. 3.1%)的析氢速率高达78 μmol·h^-1,约是纳米片组装ZnIn₂S₄光催化剂析氢速率的9倍、约是1% (w, 质量分数)Pt/ZnIn₂S₄样品析氢速率的3倍。此外,该复合光催化剂在反应中表现出良好的稳定性。荧光和电化学测试结果表明,NiCo₂S₄空心球是一种有效的助催化剂,可促进光生载流子的分离和传输,并降低析氢反应的活化能。最后,提出了NiCo₂S₄@ZnIn₂S₄光催化析氢的可能反应机理。在NiCo₂S₄@ZnIn₂S₄复合光催化剂中,具有高导电性的NiCo₂S₄助催化剂可快速接受ZnIn₂S₄上的光生电子,用以还原质子生成氢气,而电子牺牲剂TEOA捕获光生空穴,进而完成光催化氧化还原循环。该研究有望为基于纳米片为次级结构的分级空心异质结光催化剂的设计合成及其光催化制氢研究提供一定的指导。     

Nickel hydrides supported by a non-innocent diphosphine arene pincer: mechanistic studies of nickel-arene H-migration and partial arene hydrogenation

Nickel hydrides supported by a terphenyl diphosphine were synthesized and found to undergo nickel-to-arene H-transfers. Some of the resulting complexes also undergo the reverse (C-to-Ni) H-migration, indicating the potential for storing H-equivalents in this type of pincer ligand. NMR spectroscopy, single crystal X-ray diffraction, and isotopic labeling studies investigating the mechanism of these processes are discussed.     

Rh/Cr2O3 and CoOx Cocatalysts for Efficient Photocatalytic Water Splitting by Poly (Triazine Imide) Crystals

In situ photo-deposition of both Pt and CoO_x cocatalysts on the facets of poly (triazine imide) (PTI) crystals has been developed for photocatalytic overall water splitting. However, the undesired backward reaction (i.e., water formation) on the noble Pt surface is a spontaneously down-hill process, which restricts their efficiency to run the overall water splitting reaction. Herein, we demonstrate that the efficiency for photocatalytic overall water splitting could be largely promoted by the decoration of Rh/Cr₂O₃ and CoO_x as H₂ and O₂ evolution cocatalysts, respectively. Results reveal that the dual cocatalysts greatly extract charges from bulk to surface, while the Rh/Cr₂O₃ cocatalyst dramatically restrains the backward reaction, achieving an apparent quantum efficiency (AQE) of 20.2 % for the photocatalytic overall water splitting reaction.     

Imidazolium Ionic Liquids,Imidazolylidene Heterocyclic Carbenes,and Zeolitic Imidazolate Frameworks for CO2 Capture and Photochemical Reduction

Imidazolium ionic liquids (ILs), imidazolylidene N‐heterocyclic carbenes (NHCs), and zeolitic imidazolate frameworks (ZIFs) are imidazolate motifs which have been extensively investigated for CO₂ adsorption and conversion applications. Summarized in this minireview is the recent progress in the capture, activation, and photochemical reduction of CO₂ with these three imidazolate building blocks, from homogeneous molecular entities (ILs and NHCs) to heterogeneous crystalline scaffolds (ZIFs). The developments and existing shortcomings of the imidazolate motifs for their use in CO₂ utilizations is assessed, with more of focus on CO₂ photoredox catalysis. The opportunities and challenges of imidazolate scaffolds for future advancement of CO₂ photochemical conversion for artificial photosynthesis are discussed.     

Lewis Acid Accelerated Aryl Ether Bond Cleavage with Nickel: Orders of Magnitude Rate Enhancement Using AlMe3

Study of the kinetics of intramolecular aryl ether C?O bond cleavage by Ni was facilitated by access to a family of metal complexes supported by diphosphines with pendant aryl‐methyl ethers. The nature of the aryl substituents was found to have little effect on the rate of cleavage. In contrast, soluble Lewis acidic additives accelerate the aryl ether cleavage dramatically. The effect of AlMe ₃ was studied in detail, and showed an increase in rate by several orders of magnitude. Low temperature NMR spectroscopy studies demonstrate quantitative coordination of ether to Al. From the Lewis acid‐bound precursor, the activation parameters for ether cleavage are significantly lower. These findings provide a mechanistic basis for milder catalyst design for the activation of strong bonds.     

Formation of Hierarchical FeCoS2–CoS2 Double‐Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2

Hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO₂ reduction under visible light. The synthetic strategy, engaging the two‐step cation‐exchange reactions, precisely integrates two metal sulfides into a double‐shelled tubular heterostructure with both of the shells assembled from ultrathin two‐dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS₂–CoS₂ hybrid can reduce bulk‐to‐surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO₂ adsorption and surface‐dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO₂ reduction, affording a high CO‐generating rate of 28.1 μmol h^?1 (per 0.5 mg of catalyst).     

Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3?xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.