官能团化的手性联芳基单齿膦配体在不对称均相金催化反应中的应用

自2005年以来,不对称均相金催化反应研究取得了显著的进展,并在有机合成中得到了广泛应用.近年来,官能团化的联芳基单齿膦配体在金催化反应中显露头角,为不对称金催化反应提供了新的发展思路.本文综合评述了这一领域的研究进展,着重介绍了近年来利用这类配体实现的金催化不对称反应及反应过程中配体与底物间相互作用.

Iron-glutamate-silicotungstate ternary complex as highly active heterogeneous Fenton-like catalyst for 4-chlorophenol degradation

A novel iron-glutamate-silicotungstate ternary complex（FeШGluS iW） was synthesized from ferric chloride（FeI II）,glutamic acid（Glu）,and silicotungstic acid（SiW）,and used as a heterogeneous Fenton-like catalyst for 4-chlorophenol（4-CP） degradation at neutral pH value. The prepared FeШGluS iW was characterized using inductively coupled plasma atomic emission spectroscopy,thermogravimetry,Fourier-transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,X-ray diffraction,and field-emission scanning electron microscopy. The results showed that FeШGluS iW has the formula [Fe（C5H8NO4）（H2O）]2SiW 12O40？13H2O,with glutamate moiety and Keggin-structured SiW 12O404- heteropolyanion. The catalyst showed high catalytic activity in 4-CP degradation in the dark and under irradiation. Under the conditions of 4-CP 100 mg/L,FeШGluS iW 1.0 g/L,H2O2 20 mmol/L,and pH = 6.5,4-CP was completely decomposed in 40 min in the dark and in 15 min under irradiation. When the reaction time was prolonged to 2 h,the corresponding total organic carbon removals under dark and irradiated conditions were ca. 27% and 72%,respectively. The high catalytic activity of FeI IIGluS iW is resulted from hydrogen bonding of H2O2 on the FeI IIGluS iW surface. The enhanced degradation of 4-CP under irradiation arises from simultaneous oxidation of 4-CP through Fenton-like and photocatalytic processes respectively catalyzed by ferric iron and the SiW 12O404- hetropolyanion in FeШGluS iW.

Structural sensitivity of heterogeneous catalysts for sustainable chemical synthesis of gluconic acid from glucose

Gluconic acid and its derivatives have been widely used in the food and pharmaceutical industries. Conventional processes that involve the conversion of glucose into gluconic acid via fermentation present several technological shortcomings as they involve energy-intensive wastewater treatment and complex enzyme separation. Greener oxidation processes over heterogeneous metal catalysts have attracted increasing attention worldwide. Au-, Pt-and Pd-based heterogeneous catalysts have been extensively used for the chemical oxidation of glucose to gluconic acid. Bimetallic catalysts synthesized by adding either noble or inexpensive metals have also presented excellent performance for the oxidations of glucose. In particular, particle size, which has been recognized as the most important factor that affect catalytic performances, could be rationally tuned by changing the types of support and ligand as well as the synthesis conditions. In this perspective review, we summarize and critically discuss the recent advances in the structural design of mono-and bimetallic catalysts for the oxidation of glucose in aqueous media. Furthermore, the challenges of developing catalysts for the green synthesis of gluconic acid have been highlighted. This review provides alternative insights for designing effective catalytic materials for the catalytic oxidation of bio-derived oxygenates over heterogeneous catalysts.

Rational development of molecular earth-abundant metal complexes for electrocatalytic hydrogen production

For public health and environmental protection reasons,there is an urgent need to replace traditional fossil fuels with clean and renewable sources.Electrochemical splitting of water has the potential to produce clean hydrogen as a possible solution to global energy problems.This review article introduces the rational design of molecular metal complexes based on earth-abundant metals for electrocatalytic hydrogen production in water or water-organic media.Emphasis is placed on providing insight into structure-function relationships in catalytic properties for future ligand and catalyst design.

Structural and interfacial engineering of well‐defined metal‐organic ensembles for electrocatalytic carbon dioxide reduction

Electrochemical carbon dioxide reduction(CO_(2)RR)has been generally regarded as green technologies that can convert renewable energy such as sunlight and wind into fuels and valuable chemicals.However,the large‐scale implementation of CO_(2)RR is severely hindered by the lack of high‐performance CO_(2)RR electrocatalysts.Heterogeneous molecular catalysts and metal‐organic framework with well‐defined structure and high tunability of the metal centers and ligands show great promise for CO_(2)RR in terms of both fundamental understanding and practical application.Here,structural and interfacial engineering of these well‐defined metal‐organic ensembles is summarized.This review starts from the fundamental electrochemistry of CO_(2)RR and its evaluation criteria,and then moves to the heterogeneous molecular catalysts and metal‐organic framework with emphasis on the engineering of metal centers and ligands,their interaction with supports,as well as in situ reconstruction of metal‐organic ensembles.Summary and outlook are present in the end,with the hope to inspire and provoke more genuine thinking on the design and fabrication of efficient CO_(2)RR electrocatalysts.

Recent development of supported monometallic gold as heterogeneous catalyst for selective liquid phase hydrogenation reactions

The great potential of gold catalysts for chemical conversions in both industrial and environmental concerns has attracted increasing interest in many fields of research.Gold nanoparticles supported by metal oxides with high surface area have been recognized as highly efficient and effective green heterogeneous catalyst even at room temperature under normal reaction conditions,in gas and liquid phase reactions.In the present review,we discuss the recent development of heterogeneous,supported monometallic gold catalysts for organic transformations emphasizing mainly liquid phase hydrogenation reactions.Discussions on the catalytic synthesis procedures and the promoting effect of other noble metals are omitted since they are already worked out.Applications of heterogeneous,supported monometallic catalysts for chemoselective hydrogenations in liquid phase are studied including potential articles during the period 2000–2013.

Magnetic yolk-shell structured anatase-based microspheres loaded with Au nanoparticles for heterogeneous catalysis

Magnetic yolk-shell structured anatase-based microspheres were fabricated through successive and facile sol-gel coating on magnetite particles, followed by annealing treatments. Upon loading with gold nanoparticles, the obtained functional magnetic microspheres as heterogeneous catalysts showed superior performance in catalyzing the epoxidation of styrene with extraordinary high conversion （89.5%） and selectivity （90.8%） towards styrene oxide. It is believed that the construction process of these fascinating materials features many implications for creating other functional nanocomposites.

Semi-heterogeneous photo-Cu-dual-catalytic cross-coupling reactions using polymeric carbon nitrides

A merger of copper catalysis and semiconductor photocatalysis using polymeric carbon nitride(PCN)for multi-type cross-coupling reactions was developed.This dual-catalytic system enables mild C-H arylation,chalcogenation,and C-N cross-coupling reactions under visible light irradiation with a broad substrate scope.Good-to-excellent yields were obtained with appreciable site selectivity and functional group tolerance.Metal-free and low-cost PCN photocatalyst can easily be recovered and reused several times.

Diyne-linked and fully π-conjugated polymetalloporphyrin nanosheets for outstanding heterogeneous catalysis

Two-dimensional,ultrathin,robust,and fullyπ-conjugated organic nanomaterials are highly desirable for application in various fields due to their unique photoelectric characteristics and great number of exposed active sites.However,such matters combining excellent stability,fullπ-conjugation and adjustability are rare,which has become a bottleneck for their practical application.Herein,we present a novel kind of diyne-linked polymetalloporphyrin nanosheet featuring permanent porosity and fullπ-conjugation,which exhibits a high-aspect-ratio,outstanding stability and convenient tailoring for electronic structures.Importantly,the novel nanosheets with monodisperse nickel atoms were found to be outstanding heterogeneous catalyst with unprecedented catalytic activity and selectivity for 4-nitrophenol reduction to 4-aminophenol under mild conditions.The findings recommend that diynelinked polymetalloporphyrin nanosheets may offer new platforms for the conversion of photoelectricity and energy in the future.

Catalytic alkane dehydrogenations

Olefins find widespread applications in the synthesis of polyolefins and fine chemicals. With an increasing demand for olefins, the technologies for alkane dehydrogenation have drawn much attention. Several types of heterogeneous catalysts have found applications in industry for the dehydrogenation of light alkanes, mainly ethane, propane, and butane. In the past three decades, a number of transition-metal complexes,particularly pincer-ligated iridium complexes, have been developed as the homogeneous catalysts for alkane dehydrogenations. The homogeneous catalyst systems operate under much milder conditions compared with the heterogeneous systems, and some systems exhibit good activity and high regioselectivity in dehydrogenation of alkanes longer than butane.