二氧化碳多相催化加氢制C2及以上烃类和醇的研究进展

通过可再生能源得到的氢气将二氧化碳转化为高附加值的燃料和化学品,对于缓解全球变暖、改善生态环境和解决化石资源日益枯竭的难题具有重要的意义。通过加氢反应合成碳氢化合物,尤其是C₂₊烃类和含氧化合物愈来愈引起大家的研究兴趣。设计制备兼具二氧化碳活化和碳-碳键耦合的多功能催化剂仍然是一较大的挑战。本文总结了二氧化碳加氢合成长链烷烃、低碳烯烃、高级醇的最新研究进展,探讨了二氧化碳加氢所涉及的相关反应的热力学和动力学、反应机理和反应路径,并对现阶段报道的多相催化剂进行了归纳和分析,最后指出未来在二氧化碳加氢的多相催化过程中所面临的问题和发展方向。     

In Situ Preparation of CsPbBr3@CsPb2Br5 Composite Assisted with Water as a Highly Efficient and Stable Catalyst for Photothermal CO2 Hydrogenation

Lead halide perovskite has triggered a lot of research due to its superior optical properties. However, halide perovskite materials have poor environmental stabilities and are easily affected by external factors such as water and heat, resulting in structural decomposition and performance failure. Contrary to this commonplace concept, it is found that CsPbBr₃ (CPB) can convert to CsPb₂Br₅ (CP2B5) partially when meeting a small amount of water, and the CsPbBr₃@CsPb₂Br₅ (CPB@CP2B5) composite is synthesized by an in situ method accordingly. The CPB@CP2B5 composite shows an enhanced catalytic performance compared with pure CPB, as well as a dramatically synergistic effect of photo and thermal for catalytic CO₂ hydrogenation. The CO production rate of CPB@CP2B5 is determined as 69 μmol g⁻¹ h⁻¹ under light irradiation at 200 °C, which is 156.8 and 43.4 times higher than that under pure photo (0.44 μmol g⁻¹ h ⁻¹) and pure thermal (1.59 μmol g⁻¹ h ⁻¹) condition, respectively. Meanwhile, the CPB@CP2B5 sample is also stable, which shows no significant decline in the catalytic activity during 8 cycles of repeated experiments. The probable mechanism is explored by utilizing a series of in situ characterizations.     

Molecular-level Manipulation of Interface Charge Transfer on Plasmonic Metal/MOF Heterostructures

Plasmon-excited hot carriers have drawn great attention for driving various chemical reactions, but the short lifetimes of hot carriers seriously restrict the performance of plasmonic photocatalysis. Constructing plasmonic metal/metal-organic framework (MOF) heterostructures has been proved as an effective strategy to extend the lifetimes of hot carriers. Due to the high molecular tunability of MOFs, the MOF substrate in plasmonic metal/MOF heterostructures is able to capture hot electrons on the conduction band of MOF and hot holes on its valence band, and thus offers an ideal platform to separately study the detailed mechanism of hot electron and hole transfer processes. This review focuses on a molecular-level understanding of both hot-electron and hot-hole transfer at plasmonic metal/MOF interfaces. The enhanced stability and photocatalytic performance by introducing MOF substrates are discussed for plasmonic metal/MOF heterostructures. Additionally, typical characterization technologies are also proposed as powerful tools for tracking hot carrier transfer process.     

Ammonia Oxidation Enhanced by Photopotential Generated by Plasmonic Excitation of a Bimetallic Electrocatalyst

We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon resonances. Under visible-light excitation, this catalyst exhibits enhanced electrochemical ammonia oxidation kinetics, outperforming previously reported electrochemical schemes. We trace the enhancement to a photochemical potential resulting from electron–hole carriers generated in the electrocatalyst by plasmonic excitation. The photopotential responsible for enhanced kinetics scales linearly with the light intensity—a general design principle for eliciting superlative photoelectrochemical performance from catalysts comprised of plasmonic metals or hybrids. We also determine a photochemical conversion coefficient.     

Surface Plasmon Resonance‐Enhanced Visible‐NIR‐Driven Photocatalytic and Photothermal Catalytic Performance by Ag/Mesoporous Black TiO2 Nanotube Heterojunctions

Ag/mesoporous black TiO₂ nanotubes heterojunctions (Ag‐MBTHs) were fabricated through a surface hydrogenation, wet‐impregnation and photoreduction strategy. The as‐prepared Ag‐MBTHs possess a relatively high specific surface area of ≈85 m² g^?1 and an average pore size of ≈13.2 nm. The Ag‐MBTHs with a narrow band gap of ≈2.63 eV extend the photoresponse from UV to the visible‐light and near‐infrared (NIR) region. They exhibit excellent visible‐NIR‐driven photothermal catalytic and photocatalytic performance for complete conversion of nitro aromatic compounds (100 %) and mineralization of highly toxic phenol (100 %). The enhancement can be attributed to the mesoporous hollow structures increasing the light multi‐refraction, the Ti³⁺ in frameworks and the surface plasmon resonance (SPR) effect of plasmonic Ag nanoparticles favoring light‐harvesting and spatial separation of photogenerated electron–hole pairs, which is confirmed by transient fluorescence. The fabrication of this SPR‐enhanced visible‐NIR‐driven Ag‐MBTHs catalyst may provide new insights for designing other high‐performance heterojunctions as photocatalytic and photothermal catalytic nanomaterials.     

Elaborated Reaction Pathway of Photothermal Catalytic CO2 Conversion with H2O on Gallium Oxide-Decorated and -Defective Surfaces

Ga₂O₃-decorated and -defective surface models based on anatase TiO₂ have been established. The thermodynamic reaction pathways, including protonation, deoxygenation and hydroxylation steps, during CO₂ conversion with H₂O to C₁ products were calculated. The calculation results demonstrate that a Ga₂O₃ cocatalyst enhances the selective adsorption of CO₂ and slightly weakens the competitive adsorption of H₂O. The promotion effect of Ga₂O₃ on the subsequent reaction depends on the availability of protons and electrons. Free-energy calculations revealed that the basic functional site generated by Ga₂O₃ not only suppresses the back reaction of the OH group after H₂O directly provides protons but also maintains the surface defect oxygen vacancy (V_O), which promotes the reaction thermodynamics but tends to be consumed in the process. Additionally, Ga₂O₃ decoration promotes V_O formation, and the coexistence of Ga₂O₃ and V_O further decreases the reaction rate-determining step energy barrier, promoting C₁ production.     

Zeolite-Encaged Pd–Mn Nanocatalysts for CO2 Hydrogenation and Formic Acid Dehydrogenation

A CO₂-mediated hydrogen storage energy cycle is a promising way to implement a hydrogen economy, but the exploration of efficient catalysts to achieve this process remains challenging. Herein, sub-nanometer Pd–Mn clusters were encaged within silicalite-1 (S-1) zeolites by a ligand-protected method under direct hydrothermal conditions. The obtained zeolite-encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO₂ hydrogenation into formate and formic acid (FA) dehydrogenation back to CO₂ and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components, the PdMn_0.6@S-1 catalyst afforded a formate generation rate of 2151 mol_formate mol_Pd⁻¹ h⁻¹ at 353 K, and an initial turnover frequency of 6860 mol mol_Pd⁻¹ h⁻¹ for CO-free FA decomposition at 333 K without any additive. Both values represent the top levels among state-of-the-art heterogeneous catalysts under similar conditions. This work demonstrates that zeolite-encaged metallic catalysts hold great promise to realize CO₂-mediated hydrogen energy cycles in the future that feature fast charge and release kinetics.     

Efficient CO2 Hydrogenation to Formate with Immobilized Ir-Catalysts Based on Mesoporous Silica Beads

The Nozaki Ir-based CO₂ hydrogenation catalyst was successfully immobilized on post-functionalized silica beads (d=200 μm) through click chemistry. This material hydrogenates CO₂ into formic acid with turnover numbers reaching 2.8×10⁴ in a batch reactor within 24 hours, paving the way towards the design of efficient heterogeneous catalysts for this transformation.     

Exploring Opportunities for Platinum Nanoparticles Encapsulated in Porous Liquids as Hydrogenation Catalysts

The unusual combination of characteristics observed for porous liquids, which are typically associated with either porous solids or liquids, has led to considerable interest in this new class of materials. However, these porous liquids have so far only been investigated for their ability to separate and store gases. Herein, the catalytic capability of Pt nanoparticles encapsulated within a Type I porous liquid (Pt@HS-SiO₂ PL) is explored for the hydrogenation of several alkenes and nitroarenes under mild conditions (T=40 °C, P_H2=1 atm). The different intermediates in the porous liquid synthesis (i.e., the initial Pt@HS-SiO₂, the organosilane-functionalized intermediate, and the final porous liquid) are employed as catalysts in order to understand the effect of each component of the porous liquid on the catalysis. For the hydrogenation of 1-decene, the Pt@HS-SiO₂ PL catalyst in ethanol has the fastest reaction rate if normalized with respect to the concentration of Pt. The reaction rate slows if the reaction is completed in a “neat” porous liquid system, probably because of the high viscosity of the system. These systems may find application in cascade reactions, in particular, for those with mutually incompatible catalysts.     

金属催化剂光热催化CO2还原的研究进展

CO2的过量排放导致温室效应对环境的影响越来越严重,通过电催化、光催化、热催化、光热催化或光电催化将CO2还原成高附加值的化学品是解决CO2排放的有效途径.其中, CO2的光热催化转化是当前的主要研究领域之一.我们对光热催化进行了总结分类:热助光、光助热、光驱热和光热协同催化,并详细介绍相应的催化机理,总结了金属催化剂用于光热催化CO2还原的最新研究进展,最后提出了光热催化面临的挑战与展望.     

Rational Construction of an Exceptionally Stable MOF Catalyst with Metal-Adeninate Vertices toward CO2 Cycloaddition under Mild and Cocatalyst-Free Conditions

CO₂ is considered as the primary greenhouse gas, resulting in a series of serious environmental problems that affect people's life and health. Carbon capture and sequestration has been implemented as one of the most appealing pathways to control and use CO₂. Here, we rationally integrate various functional sites within the confined nanospace of a microporous metal–organic framework (MOF) material, which is constructed by mixed-ligand strategy based on metal-adeninate vertices. It not only exhibits excellent stability but also can efficiently transform CO₂ and epoxides to cyclic carbonates under mild and cocatalyst-free conditions. Additionally, this catalyst shows extraordinary recyclability for the CO₂ cycloaddition reaction.     

Efficient Coupling of Solar Energy to Catalytic Hydrogenation by Using Well‐Designed Palladium Nanostructures

A Ru³⁺‐mediated synthesis for the unique Pd concave nanostructures, which can directly harvest UV‐to‐visible light for styrene hydrogenation, is described. The catalytic efficiency under 100 mW cm^?2 full‐spectrum irradiation at room temperature turns out to be comparable to that of thermally (70 °C) driven reactions. The yields obtained with other Pd nanocrystals, such as nanocubes and octahedrons, are lower. The nanostructures reported here have sufficient plasmonic cross‐sections for light harvesting in a broad spectral range owing to the reduced shape symmetry, which increases the solution temperature for the reaction by the photothermal effect. They possess a large quantity of atoms at corners and edges where local heat is more efficiently generated, thus providing active sites for the reaction. Taken together, these factors drastically enhance the hydrogenation reaction by light illumination.     

Isotope Effects in Plasmonic Photosynthesis

The photoexcitation of plasmonic nanoparticles has been shown to drive multistep, multicarrier transformations, such as the conversion of CO₂ into hydrocarbons. But for such plasmon-driven chemistry to be precisely understood and modeled, the critical photoinitiation step in the reaction cascade must be identified. We meet this goal by measuring H/D and ¹²C/¹³C kinetic isotope effects (KIEs) in plasmonic photosynthesis. In particular, we found that the substitution of H₂O with D₂O slows hydrocarbon production by a factor of 5–8. This primary H/D KIE leads to the inference that hole-driven scission of the O−H bond in H₂O is a critical, limiting step in plasmonic photosynthesis. This study advances mechanistic understanding of light-driven chemical reactions on plasmonic nanoparticles.     

金属有机框架材料的制备及在吸附分离CO2中的应用

金属有机框架（MOFs）材料是当今的研究热点之一,是一类颇有潜力成为适用于CO₂吸附和分离的重要材料。本文从MOFs的发展及其所具有的特点、MOFs用于CO₂的吸附与分离所取得的突破性进展以及MOFs的传统合成及绿色制备方法三个方面展开论述。主要论述了MOFs适用于CO₂吸附的原理,及其相对于传统的CO₂吸附材料所具有的特点和优势,亦阐述了MOFs修饰与调变的方法。列出了MOFs用于单组分CO₂吸附及CO₂/CH₄、CO₂/N₂吸附分离的结果。同时,针对传统MOFs制备方法不适宜大规模CO₂捕集材料的生产,特别论述了机械化学合成法和新兴的潮湿矿物风化法,其均具有绿色化、无溶剂、低能耗和简单等特点,是一类较有研究价值和应用潜力的技术。随着温室效应和不可再生石化燃料的消耗等环境和能源问题的日趋严峻,研究及开发适用于CO₂捕集与封存技术的MOFs新材料迫在眉睫,且任重而道远。     

Pt0.01Fe0.05-g-C3N4催化剂高效光热催化二氧化碳还原

光热催化是一种高效利用太阳光,将二氧化碳转化为高价值产物的方法.本工作以石墨相氮化碳为载体,通过水热-浸渍两步法制备了负载铂、铁氧化物的石墨相氮化碳催化剂.该催化剂具备优异的光热转换性能,可实现7.36 mmol·h-1·gcat-1的二氧化碳还原活性和97％的一氧化碳选择性.使用X射线晶体衍射(XRD)、配备能量色散...     

Structure and Properties of Sol—Gel Derived CuNiMnZrO2 Catalysts for CO Hydrogenation

Two CuNiMnZrO2 catalysts (crystallized or non-crystallized) were prepared by co-hydrolyzing zirconium n-propoxide with Cu(NO3)2, Mn(NO3)2 and Ni(NO3)2 in an ethanol solution in the presence of diglycol. The physical and chemical properties of the catalysts were characterized using BET, XRD,TEM, XPS and CO-DRIFT techniques. It was found that the non-crystallizied CuNiMnZrO2 catalyst demonstrated highly dispersed active phases and high activity for CO adsorption, which resulted in good performance for synthesis of higher alcohols in CO hydrogenation compared to crystallized CuNiMnZrO2.     

MOF热解法制备Ni/C核壳材料及其催化苯乙炔加氢性能研究

通过水热合成法以硝酸镍和2,5-二羟基对苯二甲酸为原料成功合成Ni-MOF-74.以此为前体,在Ar气氛下热解制备了一系列介孔结构丰富、尺寸均匀的纳米Ni/C核壳催化剂.Ar气氛下通过延长热解时间（400℃,6 h）或提高热解温度（≥500℃）可以得到完全热解产物,粒子尺寸随热解温度的升高而增大.H₂-TPR结果表明随着热解温度的提高,镍与表面碳层之间的相互作用增强,材料还原性能降低.TEM和Ar离子溅射XPS给出了Ni/C纳米材料为核壳结构的直接证据.由于表面碳层的化学惰性,隔离作用和电子调控作用,使得部分镍物种能够以单质镍（Ni⁰）形式稳定存在.其次,表面碳壳的存在减弱了颗粒间的相互作用,有利于催化剂在反应体系中均匀分散.以苯乙炔选择加氢反应为探针,在高压釜式反应器中测试Ni/C的催化性能.研究发现Ni/C在苯乙炔加氢反应中表现出了非常优异的催化活性（0.833 mmol•min^-1•g_cat.^-1）和稳定性.其与几种催化剂的加氢活性由弱到强的顺序为：Ni < NiSi_x < 负载型Ni₂Si < Ni/C < Pd < Pt.     

Ag@SiO2纳米颗粒的制备及其在H2O2检测上的应用

利用柠檬酸三钠还原硝酸银制备了银纳米颗粒(AgNPs),然后通过氨水水解正硅酸乙酯(TEOS)的方法,在AgNPs上沉积SiO2,制备出以Ag为核,SiO2为壳的复合纳米颗粒(Ag@SiO2).调节TEOS用量,可以控制SiO2层的厚度.根据AgNPs的局域表面等离激元共振(LSPR)效应,将制得的Ag@SiO2颗粒用于H2O2的检测,检测下限为1μmol/L,并可以通过控制SiO2层的厚度方便地调节Ag@SiO2颗粒与H2O2反应的速率.与传统方法相比,具有简单、快速、成本低的优点.分别运用TEM、紫外-可见分光光度计对反应前后Ag@SiO2颗粒形貌及反应过程中其LSPR吸收的变化进行了表征.     

Unravelling the Promotional Effect of La2O3 in Pt/La-TiO2 Catalysts for CO2 Hydrogenation

This work reports the preparation of a La₂O₃-modified Pt/TiO₂ (Pt/La-TiO₂) hybrid through an excess-solution impregnation method and its application for CO₂ hydrogenation catalysis. The Pt/La-TiO₂ catalyst is characterized by XRD, H₂ temperature-programmed reduction (TPR), TEM, X-ray photoelectron spectroscopy (XPS), Raman, EPR, and N₂ sorption measurements. The Pt/La-TiO₂ composite starts to catalyze the CO₂ conversion reaction at 220 °C, which is 30 °C lower than the Pt/TiO₂ catalyst. The generation of CH₄ and CO of Pt/La-TiO₂ is 1.6 and 1.4 times greater than that of Pt/TiO₂. The CO₂ temperature-programmed desorption (TPD) analysis confirms the strengthened CO₂ adsorption on Pt/La-TiO₂. Moreover, the in situ FTIR experiments demonstrate that the enhanced CO₂ adsorption of Pt/La-TiO₂ facilitates the formation of the active Pt–CO intermediate and subsequently boosts the evolution of CH₄ and CO. The cycling tests reveal that Pt/La-TiO₂ shows reinforced stability for the CO₂ hydrogenation reaction because the La species can prevent Pt nanoparticles (NPs) from sintering. This work may provide some guidance on the development new rare-metal-modified hybrid catalysts for CO₂ fixation.     

Rational Design of a ZnII MOF with Multiple Functional Sites for Highly Efficient Fixation of CO2 under Mild Conditions: Combined Experimental and Theoretical Investigation

The development of efficient heterogeneous catalysts suitable for carbon capture and utilization (CCU) under mild conditions is a promising step towards mitigating the growing concentration of CO₂ in the atmosphere. Herein, we report the construction of a hydrogen-bonded 3D framework, {[Zn(hfipbba)(MA)]⋅3 DMF}_n (hfipbba=4,4′-(hexaflouroisopropylene)bis(benzoic acid)) (HbMOF 1 ) utilizing Zn^II center, a partially fluorinated, long-chain dicarboxylate ligand (hfipbba), and an amine-rich melamine (MA) co-ligand. Interestingly, the framework possesses two types of 1D channels decorated with CO₂-philic (−NH₂ and −CF₃) groups that promote the highly selective CO₂ adsorption by the framework, which was supported by computational simulations. Further, the synergistic involvement of both Lewis acidic and basic sites exposed in the confined 1D channels along with high thermal and chemical stability rendered HbMOF 1 a good heterogeneous catalyst for the highly efficient fixation of CO₂ in a reaction with terminal/internal epoxides at mild conditions (RT and 1 bar CO₂). Moreover, in-depth theoretical studies were carried out using periodic DFT to obtain the relative energies for each stage involved in the catalytic reaction and an insight mechanistic details of the reaction is presented. Overall, this work represents a rare demonstration of rational design of a porous Zn^II MOF incorporating multiple functional sites suitable for highly efficient fixation of CO₂ with terminal/internal epoxides at mild conditions supported by comprehensive theoretical studies.