Photocatalytic Formic Acid Conversion on CdS Nanocrystals with Controllable Selectivity for H2 or CO

Formic acid is considered a promising energy carrier and hydrogen storage material for a carbon‐neutral economy. We present an inexpensive system for the selective room‐temperature photocatalytic conversion of formic acid into either hydrogen or carbon monoxide. Under visible‐light irradiation (λ>420 nm, 1 sun), suspensions of ligand‐capped cadmium sulfide nanocrystals in formic acid/sodium formate release up to 116±14 mmol H₂ g_cat^?1 h^?1 with >99 % selectivity when combined with a cobalt co‐catalyst; the quantum yield at λ=460 nm was 21.2±2.7 %. In the absence of capping ligands, suspensions of the same photocatalyst in aqueous sodium formate generate up to 102±13 mmol CO g_cat^?1 h^?1 with >95 % selectivity and 19.7±2.7 % quantum yield. H₂ and CO production was sustained for more than one week with turnover numbers greater than 6×10⁵ and 3×10⁶, respectively.     

POM-Incorporated CoO Nanowires for Enhanced Photocatalytic Syngas Production from CO2

Utilizing sustainable energy for chemical activation of small molecules, such as CO₂, to produce important chemical feedstocks is highly desirable. The simultaneous production of CO/H₂ mixture (syngas) from photoreduction of CO₂ and H₂O is highly promising. However, the relationships between structure, composition, crystallinity, and photocatalytic performance are still indistinct. Here, amorphous ultrathin CoO nanowires and polyoxometalate incorporated nanowires with even lower crystallinity were synthesized. The POM-incorporated ultrathin nanowires exhibit high photocatalytic syngas production activity, reaching H₂ and CO evolution rates of 11555 and 4165 μmol g⁻¹ h⁻¹ respectively. Further experiments indicate that the ultrathin morphology and incorporation of POM both contribute to the superior performance. Multiple characterizations reveal the enhanced charge–hole separation efficiency of the catalyst would facilitate the photocatalysis.     

Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar-Energy Conversion: Current Status and Open Questions

One major challenge of future sustainable photochemistry is to replace precious and rare transition metals in applications such as energy conversion or electroluminescence by earth-abundant, cheap, and recyclable materials. This involves using coordination complexes of first row transition metals such as Cu, Cr, or Mn. In the case of iron, which is attractive due to its natural abundance, fundamental limitations imposed by the small ligand field splitting energy have recently been overcome. In this review article, we briefly summarize the present knowledge and understanding of the structure-property relationships of Fe(II) and Fe(III) complexes with excited state lifetimes in the nanosecond range. However, our main focus is to examine to which extent the ultrafast spectroscopy methods used so far provided insight into the excited state structure and the photo-induced dynamics of these complexes. Driven by the main question of how to spectroscopically, i. e. in energy and concentration, differentiate the population of ligand- vs. metal-centered states, the hitherto less exploited ultrafast vibrational spectroscopy is suggested to provide valuable complementary insights.     

POM‐Incorporated CoO Nanowires for Enhanced Photocatalytic Syngas Production from CO2

Utilizing sustainable energy for chemical activation of small molecules, such as CO₂, to produce important chemical feedstocks is highly desirable. The simultaneous production of CO/H₂ mixture (syngas) from photoreduction of CO₂ and H₂O is highly promising. However, the relationships between structure, composition, crystallinity, and photocatalytic performance are still indistinct. Here, amorphous ultrathin CoO nanowires and polyoxometalate incorporated nanowires with even lower crystallinity were synthesized. The POM‐incorporated ultrathin nanowires exhibit high photocatalytic syngas production activity, reaching H₂ and CO evolution rates of 11555 and 4165 μmol g^?1 h^?1 respectively. Further experiments indicate that the ultrathin morphology and incorporation of POM both contribute to the superior performance. Multiple characterizations reveal the enhanced charge–hole separation efficiency of the catalyst would facilitate the photocatalysis.     

Electrochemical Conversion of CO2 to Syngas with Controllable CO/H2 Ratios over Co and Ni Single‐Atom Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) to yield synthesis gas (syngas, CO and H₂) has been considered as a promising method to realize the net reduction in CO₂ emission. However, it is challenging to balance the CO₂RR activity and the CO/H₂ ratio. To address this issue, nitrogen‐doped carbon supported single‐atom catalysts are designed as electrocatalysts to produce syngas from CO₂RR. While Co and Ni single‐atom catalysts are selective in producing H₂ and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm^?2) with CO/H₂ ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single‐atom configurations for the H₂ and CO evolution. The results present a useful case on how non‐precious transition metal species can maintain high CO₂RR activity with tunable CO/H₂ ratios.     

基于金属钴配合物的均相光催化还原二氧化碳研究进展

本文综述了自20世纪80年代以来基于钴配合物的均相光催化二氧化碳还原研究成果,以钴配合物催化剂的结构分类并结合时间顺序回顾了近四十年来该领域的发展轨迹,重点总结了用于光催化二氧化碳还原研究的金属钴配合物的结构、催化活性以及光催化体系的构成等特点,分析了该领域面临的挑战并展望了未来的发展方向。     

多孔骨架固定分子催化剂催化CO2加氢制备甲酸研究进展

近年来, 大气中CO₂含量急剧增加, 导致了严重的温室效应. 将CO₂作为C1资源转化为燃料或精细化学品引起了越来越多的关注. 开发高效、 稳定、 可回收利用的催化剂成为CO₂资源化利用的关键. 在众多的CO₂加氢催化剂中, 功能性多孔骨架材料固定型分子催化剂展示出优异的性能, 成为研究的热点之一. 功能性骨架材料, 如多孔有机聚合物(POPs)、 共价有机骨架(COFs)和金属有机骨架(MOFs), 具有比表面积大、 热稳定性高和可调性等特点, 在设计合成催化剂方面发挥着重要作用. 本文介绍了POPs/COFs/MOFs多孔骨架材料固定分子催化剂的开发及在催化CO₂合成甲酸领域的最新进展.     

Iron Coordination to Hollow Microporous Metal-Free Disalphen Networks: Heterogeneous Iron Catalysts for CO2 Fixation to Cyclic Carbonates

This work shows that a hollow and microporous metal-free N,N′-phenylenebis(salicylideneimine) (salphen) network (H-MSN) can be engineered by Sonogashira coupling of [tetraiodo{di(Zn-salphen)}] building blocks with 1,4-diethynylbenzene in the presence of silica templates and by successive Zn and silica etching. Iron(III) ions could be incorporated into the H-MSN to form hollow and microporous Fe–disalphen networks (H-MFeSN) with enhanced microporosity and surface area. The H-MFeSN showed efficient catalytic performance and recyclability in the CO₂ conversion to cyclic carbonates.     

Crystal Engineering of MOF-Derived Bimetallic Oxide Solid Solution Anchored with Au Nanoparticles for Photocatalytic CO2 Reduction to Syngas and C2 Hydrocarbons

Considering that CO₂ reduction is mostly a multielectron reaction, it is necessary for the photocatalysts to integrate multiple catalytic sites and cooperate synergistically to achieve efficient photocatalytic CO₂ reduction to various products, such as C₂ hydrocarbons. Herein, through crystal engineering, we designed and constructed a metal–organic framework-derived Zr/Ti bimetallic oxide solid solution support, which was confirmed by X-ray diffraction, electron microscopy and X-ray absorption spectroscopy. After anchoring Au nanoparticles, the composite photocatalyst exhibited excellent performances toward photocatalytic CO₂ reduction to syngas (H₂ and CO production rates of 271.6 and 260.6 μmol g⁻¹ h⁻¹) and even C₂ hydrocarbons (C₂H₄ and C₂H₆ production rates of 6.80 and 4.05 μmol g⁻¹ h⁻¹). According to the control experiments and theoretical calculations, the strong interaction between bimetallic oxide solid solution support and Au nanoparticles was found to be beneficial for binding intermediates and reducing CO₂ reduction, highlighting the synergy effect of the catalytic system with multiple active sites.     

Electrocatalytic CO2 Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

Molecular catalysts (metal complexes), with molecularly defined uniform active sites and atomically precise structural tailorability allowing for regulating catalytic performance through metal- and ligand-centered engineering and elucidating reaction mechanisms via routine photoelectrochemical characterizations, have been increasingly explored for electrocatalytic CO₂ reduction (ECR). However, their poor stability and low catalytic current density are undesirable for practical applications. Heterogenizing discrete molecular catalysts can potentially surmount these issues, and the resulting integrated catalysts largely share catalytical properties with their discrete molecular counterparts, which bridge the gap between heterogeneous and homogeneous catalysis and combine their advantages. This minireview surveys advances in design and regulation of molecular catalysts such as porphyrin, phthalocyanine, and bipyridine-based metal complexes and their integrated catalytic materials for selective ECR.     

Electrochemical Conversion of CO2 to Syngas with Controllable CO/H2 Ratios over Co and Ni Single-Atom Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) to yield synthesis gas (syngas, CO and H₂) has been considered as a promising method to realize the net reduction in CO₂ emission. However, it is challenging to balance the CO₂RR activity and the CO/H₂ ratio. To address this issue, nitrogen-doped carbon supported single-atom catalysts are designed as electrocatalysts to produce syngas from CO₂RR. While Co and Ni single-atom catalysts are selective in producing H₂ and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm⁻²) with CO/H₂ ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single-atom configurations for the H₂ and CO evolution. The results present a useful case on how non-precious transition metal species can maintain high CO₂RR activity with tunable CO/H₂ ratios.     

均相催化剂催化氧气氧化生物质制备甲酸

甲酸是一种重要的化工原料,以可再生生物质为原料,通过催化氧气氧化制备甲酸具有重要意义。对于不溶于水的生物质原料的转化,采用可溶于水的均相催化剂体系证明是有效的。本文总结了均相催化剂体系(包括含钒杂多酸、含钒杂多酸+H₂SO₄、含钒杂多酸基离子液体、NaVO₃+H₂SO₄、VOSO₄、NaVO₃-FeCl₃+H₂SO₄、FeCl₃+H₂SO₄等)在催化氧气氧化生物质(包括生物质模型化合物、纤维素、木材、秸秆和玉米芯等)制备甲酸方面的研究,分析了其转化的过程和机理。最后,指出了目前催化氧化生物质制备甲酸存在的问题和挑战。     

Photocatalytic Conversion of CO(2) in Water over Layered Double Hydroxides

Have a bit of bubbly: Significant amounts of CO and O(2) gas are evolved in the photocatalytic conversion of CO(2) over layered double hydroxides (LDHs) in water. A simple mixture of the same metal hydroxides, which has the same constituent elements of the LDH, shows low activity for CO and O(2) evolution. Dissolved CO(2) gas was shown to be the source of carbon in the reaction over LDHs in water.     

Understanding the Deactivation Pathways of Iridium(III) Pyridine-Carboxiamide Catalysts for Formic Acid Dehydrogenation

The degradation pathways of highly active [Cp*Ir(κ²-N,N-R-pica)Cl] catalysts (pica=picolinamidate; 1 R=H, 2 R=Me) for formic acid (FA) dehydrogenation were investigated by NMR spectroscopy and DFT calculations. Under acidic conditions (1 equiv. of HNO₃), 2 undergoes partial protonation of the amide moiety, inducing rapid κ²-N,N to κ²-N,O ligand isomerization. Consistently, DFT modeling on the simpler complex 1 showed that the κ²-N,N key intermediate of FA dehydrogenation ( I_NH ), bearing a N-protonated pica, can easily transform into the κ²-N,O analogue ( I_NH2 ; ΔG^≠≈11 kcal mol⁻¹, ΔG ≈−5 kcal mol⁻¹). Intramolecular hydrogen liberation from I_NH2 is predicted to be rather prohibitive (ΔG^≠≈26 kcal mol⁻¹, ΔG≈23 kcal mol⁻¹), indicating that FA dehydrogenation should involve mostly κ²-N,N intermediates, at least at relatively high pH. Under FA dehydrogenation conditions, 2 was progressively consumed, and the vast majority of the Ir centers (58 %) were eventually found in the form of Cp*-complexes with a pyridine-amine ligand. This likely derived from hydrogenation of the pyridine-carboxiamide via a hemiaminal intermediate, which could also be detected. Clear evidence for ligand hydrogenation being the main degradation pathway also for 1 was obtained, as further confirmed by spectroscopic and catalytic tests on the independently synthesized degradation product 1 c . DFT calculations confirmed that this side reaction is kinetically and thermodynamically accessible.     

Cr或V掺杂的HMS在甲酸溶液中的光催化产氢性能研究

本文以过渡金属离子M(M代表Cr或V)掺杂为改性手段,通过改变掺杂量,合成了一系列分子筛光催化剂M(x)-HMS(x代表M/Si摩尔投料比)。用X-射线荧光光谱(XRF)、低温 N2 吸附-脱附、X-射线衍射(XRD)和紫外-可见吸收漫反射光谱(UV-vis)对M(x)-HMS进行了表征和分析。以高压汞灯为光源,以甲酸分解产氢为探针反应,研究了M(x)-HMS的光催化性能,发现Cr(x)-HMS和V(x)-HMS的产氢速率随组成变化呈双峰规律(均在x＝0.01和0.05时出现两个极大值),并从光催化剂的组成和结构角度给予了解释。以过渡金属离子M (M代表Cr或V)掺杂为改性手段, 通过改变掺杂量, 合成了一系列分子筛光催化剂M(x)-HMS (x代表M/Si投料摩尔比). 用X射线荧光光谱(XRF)、低温N₂吸附-脱附、X射线衍射(XRD)、紫外-可见吸收漫反射光谱(UV-vis)、高分辨透射电子显微镜(HRTEM)和X射线能量散射谱(EDXS)对M(x)-HMS进行了表征和分析. 以高压汞灯为光源, 以甲酸分解产氢为探针反应, 研究了M(x)-HMS的光催化性能, 发现Cr(x)-HMS和V(x)-HMS的产氢速率随组成变化呈双峰规律(均在x＝0.01和0.05时出现两个极大值), 并从光催化剂的组成和结构角度给予了解释.     

高硫合成气制甲硫醇钼硫基催化剂的制备

钼硫基催化剂;含硫化氢合成气;高硫合成气制甲硫醇钼硫基催化剂的制备     

Fe@Si/S-34催化剂的制备及其合成气制烯烃性能

合成气经费托合成反应直接制低碳烯烃是极具开发前景的合成气直接制烯烃技术,其关键是通过产物分布的调控提高低碳烯烃的选择性.本工作将疏水性Fe基费托合成催化剂与SAPO-34分子筛进行复合,制备了一系列不同SAPO-34分子筛含量的Fe@Si/S-34复合催化剂.采用X射线衍射、扫描电子显微镜、N₂吸附-脱附、NH₃程序升温脱附和水接触角测量仪考察了SAPO-34分子筛含量对催化剂物化性质的影响.结果表明SAPO-34分子筛的含量对催化剂的表面积、孔体积、酸性和疏水性具有显著的影响.随着SAPO-34分子筛含量的增加,催化剂的比表面积和总孔体积增加,弱酸和中强酸位点增加,疏水性减弱.催化性能评价结果表明,Fe@Si/S-34复合催化剂明显降低了C₅₊产物选择性,增加了C₂～C₄烃类的选择性,适量的SAPO-34分子筛能够显著提高C₂～C₄烯烃的选择性.本研究将Fe@Si催化剂的疏水性和SAPO-34分子筛对C₅₊烃的...