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.     

碳纳米材料及其在多相催化中的应用

碳纳米材料（包括零维、一维、二维碳纳米材料以及碳纳米孔材料）是一类新型的催化剂或催化剂载体材料,在氧化脱氢、选择加氢、合成氨、氨分解制氢以及燃料电池等多相催化领域具有广阔的应用前景。本文综述了近年来新型碳纳米材料在多相催化领域中的应用研究进展,介绍了这类催化材料的制备方法,重点阐述了碳载体的微/介观结构、掺杂、电子性质、表面性质、限域效应等对所担载的催化活性组分的分散,对反应物的扩散以及对催化反应的活性和选择性等方面的影响。     

Efficient microwave-promoted synthesis of glucuronic and galacturonic acid derivatives using sulfuric acid impregnated on silica

Monomode microwave-assisted syntheses of d-glucuronic and d-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This approach affords a variety of surface-active monoglycosylated glucofuranosidurono-6,3-lactones and disubstituted galacturonic adducts in excellent yields in less than 10 min at 85°C. This study illustrates the application of microwave heating mode, in combination with a cost-effective solid catalyst, as an efficient, selective, and eco-friendly methodology in carbohydrate chemistry.     

Transformation of Sugars into Chiral Polyols over a Heterogeneous Catalyst

Transformation of sugars, while maintaining the intrinsic stereochemical structure, is desirable. However, such a transformation requires multistep synthesis with protection and deprotection of the OH groups. Herein, a new method for selective transformation of sugar derivatives into chiral building blocks and a diol synthon, with retention of the intrinsic configuration (stereo‐ and regioselectively), is demonstrated. The method is based on the selective recognition of cis‐vicinal OH groups in sugars and leads to the one‐pot removal of the cis‐vicinal OH groups, without protection of OH groups (except the OH group of the hemiacetal group), over a heterogeneous CeO₂‐supported ReO_x and Pd (ReO_x‐Pd/CeO₂) catalyst by using H₂ as a reducing agent.     

Catalytic conversion of nitrogen-containing compounds over monolithic oxide catalysts

Several reactions of nitrogen-containing compounds (NO+NH₃+O₂; NO+C₃H₈ +O₂; NH₃+O₂) on monolithic oxide catalysts studied at the Boreskov Institute of Catalysis (BIC) during the last few years are discussed. Effective catalytic systems for the reactions listed above are described.     

Heteropoly acids as efficient acid catalysts in the one-step conversion of cellulose to sugar alcohols

Cellulose and even spruce can be converted efficiently into valuable platform chemicals via combined hydrolysis and hydrogenation in the aqueous phase. Thereby, heteropoly acids together with supported ruthenium catalysts show not only high activity but also remarkable selectivity to sugar alcohols reaching up to 81% yield of C(4) to C(6) sugar alcohols in only 7 h at 160 °C.     

Catalytic Ethanolysis of Kraft Lignin into High‐Value Small‐Molecular Chemicals over a Nanostructured α‐Molybdenum Carbide Catalyst

We report the complete ethanolysis of Kraft lignin over an α‐MoC_1?x/AC catalyst in pure ethanol at 280 °C to give high‐value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C₆–C₁₀ esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg^?1. C₆ alcohols and C₈ esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700–1400, differing in steps of 58 units, which is the weight of the branched‐chain linkage C₃H₆O in lignin. Hydrogen was found to have a negative effect on the formation of the low‐molecular‐weight products.     

Microimaging of Transient Concentration Profiles of Reactant and Product Molecules during Catalytic Conversion in Nanoporous Materials

Microimaging by IR microscopy is applied to the recording of the evolution of the concentration profiles of reactant and product molecules during catalytic reaction, notably during the hydrogenation of benzene to cyclohexane by nickel dispersed within a nanoporous glass. Being defined as the ratio between the reaction rate in the presence of and without diffusion limitation, the effectiveness factors of catalytic reactions were previously determined by deliberately varying the extent of transport limitation by changing a suitably chosen system parameter, such as the particle size and by comparison of the respective reaction rates. With the novel options of microimaging, effectiveness factors become accessible in a single measurement by simply monitoring the distribution of the reactant molecules over the catalyst particles.     

Highly Mesoporous Metal‐Organic Frameworks as Synergistic Multimodal Catalytic Platforms for Divergent Cascade Reactions

Rational engineering and assimilation of diverse chemo‐ and biocatalytic functionalities in a single nanostructure is highly desired for efficient multistep chemical reactions but has so far remained elusive. Here, we design and synthesize multimodal catalytic nanoreactors (MCNRs) based on a mesoporous metal‐organic framework (MOF). The MCNRs consist of customizable metal nanocrystals and stably anchored enzymes in the mesopores, as well as coordinatively unsaturated cationic metal MOF nodes, all within a single nanoreactor space. The highly intimate and diverse catalytic mesoporous microenvironments and facile accessibility to the active site in the MCNR enables the cooperative and synergistic participation from different chemo‐ and biocatalytic components. This was shown by one‐pot multistep cascade reactions involving a heterogeneous catalytic nitroaldol reaction followed by a [Pd/lipase]‐catalyzed chemoenzymatic dynamic kinetic resolution to yield optically pure (>99 % ee) nitroalcohol derivatives in quantitative yields.