Efficient and simple catalyst systems for dehydrogenation of formic acid (FA) to produce hydrogen are always desirable. In this work, the catalytic dehydrogenation of FA to H₂ and CO₂ by using the readily available [RhCp*Cl₂]₂ was found to be accelerated simply by the addition of halide anions, iodide being the most effective. At 60 °C, with [RhCp*Cl₂]₂ in azeotropic FA and triethylamine (TEA), the initial turnover frequency of dehydrogenation in the presence of I^– (4375 h^–1) is seven times as high as that of the reaction without additive (625 h^–1). Preliminary mechanistic studies suggest that the dehydrogenation is turnover-limited by the hydride-formation step, which could be facilitated by the presence of I^–.

Herein, hydrogenated amorphous Si (a-Si:H) covered with a thin layer of CoO_x is applied as photoanode for PEC water splitting. The thin layer of CoO_x effectively protects a-Si:H from the corrosive electrolyte and quantitative oxidation of water to oxygen was observed. A high applied bias photon-to-current efficiency of 2.34 % was achieved using an intrinsic absorber and an additional p-type layer. This work shows that a-Si:H with a sandwich-like structure, in which each layer has its own functionality, can be applied as an efficient and stable photoanode for PEC water oxidation.

Spatial separation of reduction sites and oxidation sites to inhibit the recombination of photogenerated electrons and holes plays a vital role in improving the efficiency of photocatalyst systems. It is very challenging to rationally deposit cocatalysts on the right facets (sites), namely, the reduction cocatalyst on the reduction facets (sites) and the oxidation cocatalyst on the oxidation facets (sites). Herein, we report that the reduction and oxidation cocatalysts can be selectively constructed on the different facets of p-type Cu₂O crystals with anisotropic facets, but not on the Cu₂O crystal with isotropic facets. The deposition of dual cocatalysts on the different facets resulted in a remarkable synergetic effect in the photocatalytic performance, which could be attributed to the spatial separation of the photogenerated charges between facets. Our work reports an instructive strategy for constructing high-efficiency photocatalyst systems for solar energy conversion.

Hydrogen production from the dehydrogenation of formic acid (FA) is promising. Most of the current catalysts for FA dehydrogenation are effective only in the presence of bases or additives. We report here newly developed iridium complexes containing conjugated N,N′-diimine ligands for FA dehydrogenation in water without the addition of bases or additives. A turnover frequency (TOF) of 487 500 h⁻¹ with [Cp*Ir(L1)Cl]Cl (L1=2,2′-bi-2-imidazoline) at 90 °C and a turnover number (TON) of 2 400 000 with in situ prepared catalyst from [IrCp*Cl₂]₂ and 2,2′-bi-1,4,5,6-tetrahydropyrimidine (L2) at 80 °C were obtained, the highest values reported for FA dehydrogenation to date. A mechanistic study reveals that the formation of [Ir-H] intermediate species is the rate-determining step in the catalytic cycle.

The synthesis of silica-based yolk–shell nanospheres confined with ultrasmall platinum nanoparticles (Pt NPs) stabilized with poly(amidoamine), in which the interaction strength between Pt NPs and the support could be facilely tuned, is reported. By ingenious utilization of silica cores with different surface wettability (hydrophilic vs. -phobic) as the adsorbent, Pt NPs could be confined in different locations of the yolk–shell nanoreactor (core vs. hollow shell), and thus, exhibit different interaction strengths with the nanoreactor (strong vs. weak). It is interesting to find that the adsorbed Pt NPs are released from the core to the hollow interiors of the yolk–shell nanospheres when a superhydrophobic inner core material (SiO₂Ph) is employed, which results in the preparation of an immobilized catalyst (Pt@SiO₂Ph); this possesses the weakest interaction strength with the support and shows the highest catalytic activity (88 500 and 7080 h⁻¹ for the hydrogenation of cyclohexene and nitrobenzene, respectively), due to its unaffected freedom of Pt NPs for retention of the intrinsic properties.

Short human telomeric (HT) DNA sequences form single G-quadruplex (G₄) units and exhibit structure-based stereocontrol for a series of reactions. However, for more biologically relevant higher-order HT G₄-DNAs (beyond a single G₄ unit), the catalytic performances are unknown. Here, we found that higher-order HT G₄-DNA copper metalloenzymes (two or three G₄ units) afford remarkably higher enantioselectivity (>90 % ee) and a five- to sixfold rate increase, compared to a single G₄ unit, for the Diels–Alder reaction. Electron paramagnetic resonance (EPR) and enzymatic kinetic studies revealed that the distinct catalytic function between single and higher-order G₄-DNA copper metalloenzymes can be attributed to different Cu^II coordination environments and substrate specificity. Our finding suggests that, like protein enzymes and ribozymes, higher-order structural organization is crucial for G₄-DNA-based catalysis.

Spatially resolved surface photovoltage spectroscopy (SRSPS) was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO₄ photocatalyst. Through the controlled synthesis of a single crystal with preferentially exposed {010} facets, highly anisotropic photogenerated hole transfer to the {011} facet of single BiVO₄ crystals was observed. The surface photovoltage signal intensity on the {011} facet was 70 times stronger than that on the {010} facets. The influence of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal is revealed.

Spatially resolved surface photovoltage spectroscopy (SRSPS) was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO₄ photocatalyst. Through the controlled synthesis of a single crystal with preferentially exposed {010} facets, highly anisotropic photogenerated hole transfer to the {011} facet of single BiVO₄ crystals was observed. The surface photovoltage signal intensity on the {011} facet was 70 times stronger than that on the {010} facets. The influence of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal is revealed.

A series of of amphiphilic imidazole based secondary and primary amine catalysts were synthesized and shown to be very effective with an acid cocatalyst for the asymmetric reaction of cyclohexanone to β,γ-unsaturated α-keto ester. Interestingly, primary and secondary amine catalysts show different regio-selectivities in this reaction. Under the catalysis of secondary amine 1, excellent enantioselectivities were observed for the products from direct 3+3 reactions of cyclohexanone with β,γ-unsaturated α-keto esters using water as the solvent. Moreover, the same reactants catalyzed by the primary amines 2 lead to the aldol reactions, affording the corresponding products with high diastereoselectivities and up to 97% ee. Theoretical studies on the transition states by using a model in gas phase revealed that steric effect plays an important role on different chemo-selective induction between the secondary amine 1 and primary amine 2.

Photoelectrochemical (PEC) water splitting is an ideal approach for renewable solar fuel production. One of the major problems is that narrow bandgap semiconductors, such as tantalum nitride, though possessing desirable band alignment for water splitting, suffer from poor photostability for water oxidation. For the first time it is shown that the presence of a ferrihydrite layer permits sustainable water oxidation at the tantalum nitride photoanode for at least 6 h with a benchmark photocurrent over 5 mA cm⁻², whereas the bare photoanode rapidly degrades within minutes. The remarkably enhanced photostability stems from the ferrihydrite, which acts as a hole-storage layer. Furthermore, this work demonstrates that it can be a general strategy for protecting narrow bandgap semiconductors against photocorrosion in solar water splitting.

Abundant and toxic hydrogen sulfide (H₂S) from industry and nature has been traditionally considered a liability. However, it represents a potential resource if valuable H₂ and elemental sulfur can be simultaneously extracted through a H₂S splitting reaction. Herein a photochemical-chemical loop linked by redox couples such as Fe²⁺/Fe³⁺ and I⁻/I₃⁻ for photoelectrochemical H₂ production and H₂S chemical absorption redox reactions are reported. Using functionalized Si as photoelectrodes, H₂S was successfully split into elemental sulfur and H₂ with high stability and selectivity under simulated solar light. This new conceptual design will not only provide a possible route for using solar energy to convert H₂S into valuable resources, but also sheds light on some challenging photochemical reactions such as CH₄ activation and CO₂ reduction.

Photoelectrochemical (PEC) water splitting is an ideal approach for renewable solar fuel production. One of the major problems is that narrow bandgap semiconductors, such as tantalum nitride, though possessing desirable band alignment for water splitting, suffer from poor photostability for water oxidation. For the first time it is shown that the presence of a ferrihydrite layer permits sustainable water oxidation at the tantalum nitride photoanode for at least 6 h with a benchmark photocurrent over 5 mA cm⁻², whereas the bare photoanode rapidly degrades within minutes. The remarkably enhanced photostability stems from the ferrihydrite, which acts as a hole-storage layer. Furthermore, this work demonstrates that it can be a general strategy for protecting narrow bandgap semiconductors against photocorrosion in solar water splitting.

Abundant and toxic hydrogen sulfide (H₂S) from industry and nature has been traditionally considered a liability. However, it represents a potential resource if valuable H₂ and elemental sulfur can be simultaneously extracted through a H₂S splitting reaction. Herein a photochemical-chemical loop linked by redox couples such as Fe²⁺/Fe³⁺ and I⁻/I₃⁻ for photoelectrochemical H₂ production and H₂S chemical absorption redox reactions are reported. Using functionalized Si as photoelectrodes, H₂S was successfully split into elemental sulfur and H₂ with high stability and selectivity under simulated solar light. This new conceptual design will not only provide a possible route for using solar energy to convert H₂S into valuable resources, but also sheds light on some challenging photochemical reactions such as CH₄ activation and CO₂ reduction.

The nature and location of copper in Cu/SSZ-13 zeolites synthesized by using a one-pot hydrothermal approach with Cu–tetraethylenepentamine as a template and by the ion exchange of SSZ-13 were investigated by applying H₂-temperature-programmed reduction, FTIR, EPR, and in situ Raman spectroscopic techniques. The one-pot synthesized Cu/SSZ-13 zeolite contains predominantly isolated copper ions in the large cages, whereas copper species in the ion-exchanged Cu/SSZ-13 zeolite occupy sites in the large cages of the chabazite (CHA) structure and the six-membered rings of the CHA structure. If the one-pot synthesized Cu/SSZ-13 zeolite is exchanged with the NH₄NO₃ solution in addition to the removal of a part of copper ions, the remaining copper ions in the CHA structure relocated from the large cages to the six-membered rings. Isolated copper dominated in all Cu/SSZ-13 zeolites. The in situ Raman spectra demonstrated that CuOCu dimers form at higher copper content. The bis-μ-oxo dicopper(III) complex is observed only in the ion-exchanged sample upon dehydration. The higher NO selective catalytic reduction activity of the one-pot synthesized sample in a wide temperature range appears to be due to the predominance of isolated Cu²⁺ sites in the large cages, and their higher reactivity is possibly owing to the lower stability of Cu²⁺ at these sites.

A facile colloidal approach to synthesize Ag₈(Ge_1−x,Sn_x)(S_6−y,Se_y) nanocrystals (NCs) in a highly controlled way across the entire compositional ranges (0≤x≤1, 0≤y≤6) has been developed. The NCs exhibit a uniform size distribution, highly crystalline structure, over 1 g scalable synthesis, and tunable band gaps in the range of 0.88–1.45 eV by varying their chemical compositions. The Ag₈GeS₆ NCs with a band gap of approximately 1.45 eV were employed as a model light harvester to assess their applicability in solar cells by a full solution-processing device, yielding an efficiency of 0.28 % under AM1.5 illumination, demonstrating their application potential in solar energy utilization.

Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole-based isotetronic acids and 5-1H-pyrrol-2-ones.The asymmetric 1,2-addition reactions of α-ketoesters to isatins and imines by using an acid–base bifunctional 6′-OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5-1H-pyrrol-2-ones, respectively, in excellent optical purities (up to 98 % ee). FT-IR analysis supported the existence of hydrogen-bonding interaction between the 6′-OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol.

Density functional theory (DFT) calculations are used to explore water adsorption and activation on different α-Ga₂O₃ surfaces, namely (001), (100), (110), and (012). The geometries and binding energies of molecular and dissociative adsorption are studied as a function of coverage. The simulations reveal that dissociative water adsorption on all the studied low-index surfaces are thermodynamically favorable. Analysis of surface energies suggests that the most preferentially exposed surface is (012). The contribution of surface relaxation to the respective surface energies is significant. Calculations of electron local density of states indicate that the electron-energy band gaps for the four investigated surfaces appears to be less related to the difference in coordinative unsaturation of the surface atoms, but rather to changes in the ionicity of the surface chemical bonds. The electrochemical computation is used to investigate the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on α-Ga₂O₃ surfaces. Our results indicate that the (100) and (110) surfaces, which have low stability, are the most favorable ones for HER and OER, respectively.

Two polythiophene derivatives using fluorine atoms and hexyl or hexyloxy group as electron-withdrawing and donating substituents have been synthesized. The introduction of fluorine atoms to the polythiophene backbones simultaneously lowers the HOMO and narrows the bandgap, and the stronger electron-donating ability of hexyloxy side chain further reduces the bandgap. As a result, poly[3-hexylthiophene-2,5-diyl-alt-3,4-difluorothiophene] (PHTDFT) shows HOMO and bandgap of −5.31/1.83 eV and poly[3,4-dihexyloxythiophene-2,5-diyl-alt-3,4-difluorothiophene] (PDHOTDFT) shows HOMO and bandgap of −5.14/1.68 eV, both are lower than −4.76/2.02 eV of P3HT. Benefiting from the lower HOMO, PHTDFT:PC₆₁BM (1:1) polymer solar cells obtain a power conversion efficiency of 1.11% and an impressed open-circuit voltage of 0.79 V under solar illumination AM1.5 (100 mW/cm²).

By taking advantage of UV-Raman spectroscopy and high-resolution TEM (HRTEM), combined with the focused ion beam (FIB) technique, the transformation from GaOOH into α-Ga₂O₃ and then into β-Ga₂O₃ was followed. We found that the stepwise transformations took place from the surface region before developing into the bulk of single particles without particle agglomeration and growth. During the transformation from GaOOH into α-Ga₂O₃, the elimination of water vapor through the dehydroxylation of GaOOH resulted in the formation of micropores in the single particles, whilst maintaining their particle size. For the phase transformation from α-Ga₂O₃ into β-Ga₂O₃, the nucleation of β-Ga₂O₃ was found to occur at the surface defects and this process could be retarded by occupying these defects with a small amount of La₂O₃. By finely controlling the process of the phase transformation, the β-Ga₂O₃ domains gradually developed from the surface into the bulk of the single particles without particle agglomeration. Therefore, the surface structure of the α-Ga₂O₃ single particles can be easily tuned and a particle with an α@β core–shell phase structure has been obtained.

Microporous vanadosilicates with octahedral VO₆ and tetrahedral SiO₄ units, better known as AM-6, have been hydrothermally synthesized with different morphologies by controlling the Na/K molar ratio of the initial gel mixtures. The morphology of the AM-6 materials changed from bulky cube to nanofiber aggregates as the Na/K molar ratio decreased from 1.9 to 0.2. Raman spectroscopy revealed that the VO₃⁻ intermediate species plays an important role in the formation of the nanofiber morphology. The orientation of -V-O-V- chains in nanofiber aggregates was examined by confocal polarized micro-Raman spectroscopy. It was found that these aggregates are assemblies of short -V-O-V- chains perpendicular to the axis of nanofibers. The obtained AM-6 nanofibers greatly increase the exposed proportion of VO terminals, and thus improve the catalytic performance.

Macromolecular crowding is an ubiquitous phenomenon in living cells that significantly affects the function of enzymes in vivo. However, this effect has not been paid much attention in the research of the immobilization of enzymes onto mesoporous silica. Herein, we report the combined effects of macromolecular crowding and surface hydrophobicity on the performance of an immobilized enzyme by accommodating lipase molecules into a series of mesoporous silicas with different amounts of inert poly(methacrylate) (PMA) covalently anchored inside the nanopores. The incorporation of the PMA polymer into the nanopores of mesoporous silica enables the fabrication of a crowded and hydrophobic microenvironment for the immobilized enzyme and the variation in polymer content facilitates an adjustment of the degree of crowding and surface properties of this environment. Based on this system, the catalytic features of immobilized lipase were investigated as a function of polymer content in nanopores and the results indicated that the catalytic efficiency, thermostability, and reusability of immobilized lipase could all be improved by taking advantage of the macromolecular crowding effect and surface hydrophobicity. These findings provide insight into the possible functions of the macromolecular crowding effect, which should be considered and integrated into the fabrication of suitable mesoporous silicas to improve enzyme immobilization.

The oxygen evolution reaction (OER) is regarded as one of the key issues in achieving efficient photocatalytic water splitting. Monoclinic scheelite BiVO₄ is a visible-light-responsive semiconductor which has proved to be effective for oxygen evolution. Recently, the synthesis of a series of monoclinic BiVO₄ single crystals was reported, and it was found that the (010), (110), and (011) facets are highly exposed and that the photocatalytic O₂ evolution activity depends on the degree of exposure of the (010) facets. To explore the properties of and photocatalytic water oxidation reaction on different facets, DFT calculations were performed to investigate the geometric structure, optical properties, electronic structure, water adsorption, and the whole OER free-energy profiles on BiVO₄ (010) and (011) facets. The calculated results suggest both favorable and unfavorable factors for OER on the (010) and the (011) facets. Due to the combined effects of the above-mentioned factors, different facets exhibit quite different photocatalytic activities.

Two chiral sulfur compounds, tert-butyl tert-butanethiosulfinate (1) and tert-butanesulfinamide (2), with inversion of configuration, have been studied by Raman optical activity (ROA) and electronic circular dichroism combined with density functional theory calculation. With the S–S linkage in 1, the couplings between the two tertiary carbon atoms often generate large ROA signals, whereas the tertiary carbon atom itself generally makes a large contribution to ROA signals in 2 for similar vibrational modes. The conformational dependence of ROA parameters provides probing conformation around the S–S bond from a new perspective. The simultaneous use of electronic circular dichroism and ROA is warranted to extract reliable conformational information. ROA provides a suitable candidate for the stereochemical study of chiral sulfur compounds, especially its capability of sensing the conformation around the S–S bond. Chirality 24:731–740, 2012. © 2012 Wiley Periodicals, Inc.

Pd-doped propyl sulfonic acid-functionalized hollow nanospheres proved to be efficient bifunctionalized catalysts for the one-pot synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen in liquid phase. These hollow nanospheres exhibited a higher activity than their bulk mesoporous counterparts (SBA-15 or FDU-12), mainly due to the short diffusion resistance of hollow nanospheres. Hollow nanospheres with silica frameworks showed higher activity and selectivity for MIBK than those with ethane-bridged frameworks, suggesting that hollow nanospheres with hydrophilic surface properties favor the formation of MIBK. This is probably due to the increased affinity of the hydrophilic surface towards acetone and its decreased affinity towards MIBK, which precludes deep condensation of MIBK with acetone. Under optimal conditions, up to 90 % selectivity for MIBK can be obtained with conversions of acetone as high as 43 %. This result is among the best reported so far for mesoporous silica-based catalysts. The control/fine-tuning of morphology and surface properties provides an efficient strategy for improving the catalytic performance of solid catalysts.

The mechanism of crystallization of microporous titanosilicate ETS-10 was investigated by Raman spectroscopy combined with ²⁹Si magic-angle spinning (MAS) NMR spectroscopy, DFT calculations, and SEM imaging. The formation of three-membered ring species is shown to be the key step in the hydrothermal synthesis of ETS-10. They are formed by means of a complex process that involves the interaction of silicate species in the reaction mixture, which promotes the dissolution of TiO₂ particles. These insights into the mechanism of ETS-10 growth led to the successful development of a new synthesis route to the vanadosilicate AM-6 that involves the use of intermediates that contain three-membered ring species as an initiator.

A thorough investigation of the active titanium species in TS-1 zeolite was conducted by in situ UV resonance Raman spectroscopy combined with UV/Vis diffuse reflectance spectroscopy, DFT calculations, and epoxidation experiments. A new titanium species was identified with a characteristic Raman band at 695 cm⁻¹ when excited at the 266 nm laser line. It is shown that the newly found titanium species is active in the epoxidation reactions in addition to the tetrahedrally coordinated titanium species. However, the acidity of the new titanium species could catalyze the ring-opening reactions of the epoxy products. It results in a lower selectivity toward the epoxy products relative to that of the tetrahedrally coordinated titanium species. The side reaction can be suppressed by the addition of a weak basic reagent.

MIL-101, a chromium-based metal–organic framework, is known for its very large pore size, large surface area and good stability. However, applications of this material in catalysis are still limited. 5-Hydroxymethylfurfural (HMF) has been considered a renewable chemical platform for the production of liquid fuels and fine chemicals. Phosphotungstic acid, H₃PW₁₂O₄₀ (PTA), encapsulated in MIL-101 is evaluated as a potential catalyst for the selective dehydration of fructose and glucose to 5-hydroxymethylfurfural. The results demonstrate that PTA/MIL-101 is effective for HMF production from fructose in DMSO and can be reused. This is the first example of the application of a metal–organic framework in carbohydrate dehydration.

UV–Raman and NMR spectroscopy, combined with other techniques, have been used to characterize crystallization of zeolite A. In situ UV–Raman spectroscopy shows that the starting gel for crystallization of zeolite A contains a lot of four-ring (4R) building units and the appearance of six-ring (6R) building blocks is the signal for crystal formation. ²⁹Si NMR spectroscopy results suggest that the starting gel is double four-ring (D4R) rich and during crystallization of zeolite A both α and β cages appear. ²⁷Al NMR spectroscopy results indicate the absence of Al (2Si) species in the starting gel, suggesting the absence of single 4R building units in the starting gel. Furthermore, composition analysis of both solid and liquid samples shows that the solid rather than liquid phase predominates for the crystallization of zeolite A. Therefore, it is proposed that the crystallization of zeolite A mainly occurs in the solid phase by self-assembly or rearrangement starting from the zeolite building units mainly consisting of D4R. The essential role of D4R is directly confirmed by successful conversion from a solution of D4R to zeolite A in the presence of NaCl, and the importance of solid phase is reasonably demonstrated by the successful synthesis of zeolite A from a dry aluminosilicate gel. By considering that the solid phase has a major contribution to crystallization, a novel route was designed to synthesizing zeolite A from the raw materials water glass (Na₂SiO₃ in aqueous solution) and NaAlO₂, without additional water and NaOH; this route not only simplifies synthetic procedures, but reduces water consumption.

Monoclinic BiVO₄ crystals with preferentially exposed (040) facets were hydrothermally synthesized by using a trace amount of TiCl₃ as the directing agent; this function was confirmed by X-ray diffraction patterns (XRD) and high-resolution transmission electron microscopy (HRTEM). The effects of the directing agent TiCl₃ and the pH values applied during synthesis have been studied, and the optimized BiVO₄ sample with highly exposed (040) facet could be obtained by using 1.2 at. % of TiCl₃ as the directing agent at a pH value of 2. Some complementary techniques were also applied to exclude the effects of the structural and physical property changes, such as surface area and hydrophilicity. The photocatalytic activity of oxygen evolution on BiVO₄ is found to be proportionally correlated with the exposed surfaces of the (040) facet. It is assumed that the active sites with a BiV₄ structure on the exposed (040) facet is assigned to be responsible for the high activity of O₂ evolution.

(R)-(+)-1,1′-Bi-2-naphthol ((R)-(+)-Binol)-functionalized (Binol=2,2′-dihydroxy-1,1′-binaphthyl) chiral mesoporous organosilica nanospheres with uniform particle size (100 to 300 nm) have been synthesized by co-condensation of tetraethoxysilane and (R)-2,2′-di(methoxymethyl)oxy-6,6′-di(1-propyl trimethoxysilyl)-1,1′-binaphthyl in a basic medium with cetyltrimethylammonium bromide as the template. Nanospheres with a radiative 2D hexagonal channel arrangement exhibit higher enantioselectivity and turnover frequency than those with a penetrating 2D hexagonal channel arrangement (94 versus 88 % and 43 versus 15 h⁻¹, respectively) in the asymmetric addition of diethylzinc to aldehydes. In addition, under similar conditions, the enantioselectivity of the nanospheres can be greatly improved as the structural order of the framework increases. These results clearly show that the structural order of nanospheres affects enantioselective reactions. The enantioselectivity of the nanospheres synthesized by the co-condensation method is higher than that of nanospheres prepared by a grafting method and even higher than that of their homogeneous counterpart. These results indicate that the bite angle of (R)-(+)-Binol bridging in a more rigid porous network is in a more favorable position for achieving higher enantioselectivity. The efficiency of a co-condensation method for the synthesis of high-performance heterogeneous asymmetric catalysts is also reported.

Recently, the field of heterogeneous asymmetric catalysis, generally using chiral solid catalysts, has attracted much attention in the production of single enantiomers. Among versatile chiral solid catalysts, chiral metal complexes confined in nanoreactors often exhibit very unique enantioselectivity and catalytic activity compared to homogeneous catalysts. In this Focus Review, we summarize the recent advances in asymmetric reactions on chiral metal complexes confined in nanoreactors with an emphasis on the confinement effect and cooperative activation effect of the nanoreactor and new strategies for the preparation of chiral solid catalysts, such as the encapsulation of chiral metal complexes in the nanocages of mesoporous silica and incorporation of chiral ligands in the network of mesoporous organosilicas.