Enhancement Of Catalytic Efficiency Research Articles

Carbon-dot liposome–based synthesis of gold nanocatalysts for efficient reduction of 4-nitrophenol in wastewater

Supported metal nanoparticles (NPs) having high catalytic activity and stability hold great promise in many fields including catalytic wastewater treatment. These NPs can be effectively stabilized by the suitable carriers to achieve satisfactory long-term stability and increased recyclability. Compared with common solid-state supports, catalyst supports with dynamic behavior are expected to endow active sites with additional degrees of freedom for enhanced catalytic performance. Here, a novel dynamical nanocatalyst support utilizing lamellar vesicles formed via self-assembly of lipid-like carbon dots was devised for in situ growth of gold NPs decorated carbon-dot liposomes (AuNPs@CDLs) in catalytic reduction application. CDLs with abundant carbon domains and surface functional groups are ideal hosts for carrying high-density Au NPs, which are beneficial for providing large number of active sites. CDLs also endow high substrate entrapment and adsorption capacity and thereby improve the overall catalytic performance. Our results reveal that AuNPs@CDLs exhibited superior catalytic activity than unsupported Au NPs for catalytic reduction of 4-nitrophenol (4-NP) with sodium borohydride. The increased fluidity in the vesicle membrane also leads to an enhancement of catalytic efficiency. AuNPs@CDLs have been successfully applied in industrial wastewater treatment, with results of almost complete degradation of 4-NP within 3 min. As a dynamically self-assembled support, CDLs can not only improve the stability against salt-induced aggregation and reusability of immobilized metal nanocatalysts, but also enhance the accessibility of active sites through the intrinsic fluidity of vesicle membranes.

Collaborative integration of Fe-Nx active center into defective sulfur/selenium-doped carbon for efficient oxygen electrocatalysts in liquid and flexible Zn-air batteries

Strategic active site organization is imperative for the advancement of effective and long-lasting catalysts of oxygen reduction reactions. However, the controllable multi-active site design is a highly intricate topic for catalyst synthesis. Employing pre-trapping and post-activation strategy, Fe-N bonding structure and S, Se functionalized heteroatom are integrated into a conductive porous carbon. In this process, the nitrogen-abundant polymer 1,3,5-triformylbenzene-tris(4-aminophenyl)benzene (Tf-TAPA) adsorbs Fe3+ under the intrinsically metal anchoring ability of N atoms and simultaneously in-situ assembles long-chain thiophene-S. Subsequently, the Fe3+ is transformed into Fe-Nx moieties with the conversion of the organic chain to incompletely graphitized carbon. Furthermore, the alteration of the electronic configuration achieved through the introduction of dual-atom S and Se leads to a pronounced enhancement in catalytic efficiency. Benefitting from the Fe-Nx bonding structure, dense structural defects, and conductive carbon networks, the resultant Fe-S,Se/NCNs possesses a positive half-wave potential of 0.86 V and a 90% current retention rate, outstripping the Pt/C benchmark. Moreover, the liquid and flexible ZAB driven by Fe-S,Se/NCNs achieves large power densities of 259.7 and 164.7 mW/cm2, respectively. This study provides a new comprehension in developing an efficient and stable M-N-C oxygen electrocatalyst.

Boosting Photocatalytic Performance of ZnO Nanowires via Building Heterojunction with g-C3N4.

The development of a stable and highly active photocatalyst has garnered significant attention in the field of wastewater treatment. In this study, a novel technique involving a facile stirring method was devised to fabricate an array of g-C3N4/ZnO nanowire (ZnO NW) composites. Through the introduction of g-C3N4 to augment the generation of electron-hole pairs upon exposure to light, the catalytic efficacy of these composites was found to surpass that of the pristine ZnO NWs when subjected to simulated sunlight. The photocatalytic performance of a 20 mg·L-1 methylene blue solution was found to be highest when the doping rate was 25 wt%, resulting in a degradation rate of 99.1% after 60 min. The remarkable enhancement in catalytic efficiency can be ascribed to the emergence of a captivating hetero-junction at the interface of g-C3N4 and ZnO NWs, characterized by a harmoniously aligned band structure. This alluring arrangement effectively curtailed charge carrier recombination, amplified light absorption, and augmented the distinct surface area, culminating in a notable boost to the photocatalytic prowess. These findings suggest that the strategic engineering of g-C3N4/ZnO NW heterostructures holds tremendous promise as a pioneering avenue for enhancing the efficacy of wastewater treatment methodologies.

Enhancement in the catalytic efficiency of D-amino acid oxidase from Glutamicibacter protophormiae by multiple amino acid substitutions

D-Amino acid oxidase (DAAO) is an imperative oxidoreductase that oxidizes D-amino acids to corresponding keto acids, producing ammonia and hydrogen peroxide. Previously, based on the sequence alignment of DAAO from Glutamicibacter protophormiae (GpDAAO-1) and (GpDAAO-2), 4 residues (E115, N119, T256, T286) at the surface regions of GpDAAO-2, were subjected to site-directed mutagenesis and achieved 4 single-point mutants with enhanced catalytic efficiency (kcat/Km) compared to parental GpDAAO-2. In the present study, to further enhance the catalytic efficiency of GpDAAO-2, a total of 11 (6 double, 4 triple, and 1 quadruple-point) mutants were prepared by the different combinations of 4 single-point mutants. All mutants and wild types were overexpressed, purified and enzymatically characterized. A triple-point mutant E115A/N119D/T286A exhibited the most significant improvement in catalytic efficiency as compared to wild-type GpDAAO-1 and GpDAAO-2. Structural modeling analysis elucidated that residue Y213 in loop region C209-Y219 might act as the active-site lid for controlling substrate access, the residue K256 substituted by threonine (K256T) might change the hydrogen bonding interaction between residue Y213 and the surrounding residues, and switch the conformation of the active-site lid from the closed state to the open state, resulting in the enhancement in substrate accessibility and catalytic efficiency.

Front Cover: Engineering a Medium‐chain Alcohol Dehydrogenase for Efficient Synthesis of (S)‐N−Boc‐3−pyrrolidinol by Adjusting the Conformational Dynamics of Loops (ChemCatChem 5/2023)

The Front Cover shows that a medium-chain alcohol dehydrogenase modified in the loop is efficiently catalyzing N-Boc-3-pyrrolidone to produce (S)-N-Boc-3-pyrrolidinol. In their Research Article, H. Wang and co-workers proposed that loop-loop interaction region acts like the “bridges” between loops and could be used to adjust conformational dynamics of the enzyme, thus modifying its catalytic efficiency. Combined with the analysis of residue orientation and interaction network, three loop-loop interaction regions were selected for mutagenesis. After screening, a mutant with 94.5-fold enhancement in catalytic efficiency was obtained. The results show that the residues located in the loop-loop interaction region could be used to effectively alter the loop conformation, thereby affecting the catalytic properties of the enzyme. More information can be found in the Research Article by H. Wang and co-workers.

Coenzyme Engineering of Glucose-6-phosphate Dehydrogenase on a Nicotinamide-Based Biomimic and Its Application as a Glucose Biosensor

Nicotinamide adenine dinucleotide (NAD(P)+)-dependent oxidoreductases have been widely employed as biocatalysts for numerous applications, such as in vitro biomanufacturing and biosensors. The application of biomimetic nicotinamide coenzymes (BNCs) in an enzymatic redox cascade constitutes a promising alternative that can eliminate the need for expensive natural NAD(P)+ coenzymes. Herein, we demonstrated that the coenzyme engineering of glucose-6-phosphate dehydrogenase from Zymomonas mobilis (ZmG6PDH) enhanced its catalytic efficiency (kcat/Km) on oxidized nicotinamide mononucleotide (NMN+). Compared with the wild-type (WT) enzyme, the optimal mutant R4 exhibited a 112-fold enhancement in catalytic efficiency on NMN+, with 4.7 × 103 and 2.6 × 103-fold change in the two coenzyme specificity values ([kcat/Km]NMN+/[kcat/Km]NAD+ and [kcat/Km]NMN+/[kcat/Km]NADP+), respectively. To obtain insights into the structure–function relationship of the enzyme and its mutant, we determined the crystal structures of WT G6PDH (apo-WT) and the complex of mutant R4 and NMN+ (R4:NMN+) and performed molecular dynamics simulations of the ternary complexes of the G6PDH/substrate (glucose-6-phosphate, G6P)/coenzyme. The results revealed that the helix region of the coenzyme-binding Rossmann-like domain in mutant R4 was nearer to the active site than the wild-type enzyme, thus creating a more compact substrate/coenzyme-binding site to favor the binding of the substrate G6P and NMN+. Furthermore, a glucose biosensor based on the glucokinase (GK)/G6PDH-NMN+ biosystem without cryopreservation was constructed using NMN+ as the coenzyme. These results indicate that the combination of BNCs and oxidoreductases can be widely employed in biosensors, biocatalysis, and in vitro biomanufacturing.

Engineering of Hydroxymandelate Oxidase and Cascade Reactions for High-Yielding Conversion of Racemic Mandelic Acids to Phenylglyoxylic Acids and (R)- and (S)-Phenylglycines

An alcohol oxidase (AOx) for the (S)-enantioselective oxidation of 4-hydroxymandelic acid (4-HMA) to 4-hydroxyphenylglyoxylic acid (4-HPGA) with enhanced activity was developed by directed evolution of hydroxymandelate oxidase (HMO) through three rounds of iterative saturation mutagenesis. The engineered HMO mutant A80G-T159S-T162Q (HMOTM) catalyzed the oxidation of (S)-4-HMA to 4-HPGA with a 23-fold enhancement in catalytic efficiency (kcat/KM). Substrate docking simulation on HMOTM suggested that A80G reoriented FMN, while T159S and T162Q formed hydrogen bonds with the carboxylic group of the substrate, thus facilitating substrate binding and catalysis. (S)-Enantioselective HMOTM was used together with mandelic acid racemase (MR) and catalase (KatE) to achieve high-yielding oxidation of rac-4-HMA to 4-HPGA with either purified enzymes (up to 93% yield and 426 mM) or Escherichia coli (HMC) cells expressing the three enzymes (up to 93% yield and 140 mM). The HMOTM-MR-KatE cascades were applied for the oxidation of seven other substituted MAs, producing the corresponding phenylglyoxylic acids with 90–99% conversions using purified enzymes or whole cells. Efficient conversion of racemic α-hydroxy acids to (S)- or (R)-α-amino acids was achieved by combining HMOTM-MR-KatE with (S)-enantioselective transaminase (EcαTA) or (R)-enantioselective transaminase (DpgAT), together with glutamate dehydrogenase (GluDH). Coupling of E. coli (HMC) with E. coli (E-G) expressing EcαTA and GluDH for one-pot biotransformation of five rac-MAs produced the corresponding (S)-phenylglycines (PGs) in 91–99% ee with 73–98% conversions. Using E. coli (HMC) and E. coli (D-G) expressing DpgAT and GluDH enabled the production of five (R)-PGs with 93–99% ee and 73–98% conversions from the corresponding rac-MAs. The engineered AOx, AOx-MR-KatE cascades, and AOx-MR-Kat-GluDH-(S)- or (R)-TA cascades provide useful tools for highly active and enantioselective oxidation of racemic hydroxyacids and high-yielding conversion of racemic hydroxyacids to ketoacids and enantiopure (S)- or (R)-aminoacids, respectively, which are challenging and useful chemical reactions.

Engineering a Medium‐chain Alcohol Dehydrogenase for Efficient Synthesis of (S)‐N−Boc‐3−pyrrolidinol by Adjusting the Conformational Dynamics of Loops

AbstractLoops typically allosterically communicate with active sites, and their conformational dynamics can affect the catalytic properties of enzymes. Herein, by manipulating the loop conformational dynamics via adjusting loop‐loop interactions, a medium‐chain alcohol dehydrogenase (Syn94) was engineered to enhance the activity without enantioselectivity reduction. Syn94, from Synechocystis sp. PCC 6803 was identified, and it demonstrated good enantioselectivity (>99.9 % ee) for synthesizing (S)‐N−Boc‐3−pyrrolidinol ((S)‐Boc−PL), a key intermediate of darifenacin, but with low catalytic efficiency. To enhance its activity, three regions for loop‐loop interactions near the active pocket were identified for mutagenesis. After the iteration of two effective sites, the best mutant, S89T/P282R, with a 94.5‐fold enhancement in catalytic efficiency, was successfully obtained. By establishing a co‐expression system of S89T/P282R and glucose dehydrogenase (GDH), up to 1.0 M (180.2 g/L) substrate could be completely reduced to (S)‐Boc−PL within 7 h, with 617 g/L/d space‐time‐yield. Molecular dynamics simulations revealed that the enhanced activity was related to the stabilization of two loops, D41‐V58 and W87‐T112.

Recent advances in catalyst design and activity enhancement induced by a magnetic field for electrocatalysis

This review summarizes the current understanding of magnetic field-assisted synthesis of catalysts and enhancement of catalytic efficiency, including modulation of surface electronic structure, and electron spin state regulation mechanisms.

Light-induced hydrogen production from water using nickel(II) catalysts and N-doped carbon-dot photosensitizers: catalytic efficiency enhancement by increase of catalyst nuclearity.

Solar energy conversion to chemical energy via light-induced H2O splitting to O2 and H2 is considered to be a promising solution to meet the growing global energy demands. To make this transformation economically viable, it is necessary to develop sustainable photocatalytic systems. Herein, we present an efficient photocatalytic H2 production system which relies on components comprised of low-cost and high-abundance elements. In particular, a series of mononuclear complexes [Ni(LNS)3]- and [Ni(N^N)(LNS)2] and a hexanuclear complex [Ni(LNS)2]6 (N^N = diimine and LNS- = heterocyclic thioamidate with different group-substituents) were synthesized and utilized as catalysts, in combination with N-doped carbon dots as photosensitizer, for efficient H2 evolution from aqueous protons. Differences in H2 production efficiency were observed among the studied Ni(II) catalysts, with complexes bearing ligands with stronger electron-donating ability exhibiting higher catalytic activity. A remarkable catalytic efficiency enhancement was observed for the hexanuclear complex, with catalyst loadings lower than those of the mononuclear Ni(II) complexes, affording TONs >1550 (among the highest values reported for photocatalytic systems of similar type operating in H2O). These data provide an indication of catalytic cooperativity between the metal centers of the hexanuclear complex, and demonstrate the crucial role of atomically precise polynuclear Ni(II) catalysts in light-induced H2 production, a result that can guide future catalyst design towards the development of highly efficient, low-cost and environmentally benign photocatalytic systems.

Chalcogen composition driven enhancement of catalytic efficiency in zirconium based monolayers: insight from reaction coordinate mapping

Exploring the bifunctional catalytic activity of zirconium dichalcogenides monolayers for hydrogen production through water splitting process.

Nickel decorated on Platinum Confined in MXene as an Electrocatalyst for enhanced Electrooxidation of Methanol

The architecture and evaluation of a potent, cost-efficient anode catalyst for methanol oxidation reactions (MOR) have great significance in Direct Methanol Fuel Cells (DFMC) applications. In this study, Ni decorated Pt confined into the layers of 2D Transition metal carbides–MXenes were synthesized and used as electrocatalyst for MOR. Pt-Ni/MXene electrocatalyst was prepared via wet impregnation method utilizing NaBH4 as a reducing agent. The Pt-Ni/MXene nanocomposite formation was verified through XRD, SEM, EDX, TEM, and BET, XPS analysis. Cyclic voltammetry, Chronoamperometric, and electrochemical impedance spectroscopy analysis revealed the Electrochemical performance of Pt-Ni/MXene for electrooxidation of methanol. The synergistic effect of Ni decorated Pt and MXene nanoparticles offered improved durability (84.7 % of retention after 400 cycles) for the Pt-Ni/MXene electrocatalyst for MOR. The electrochemical performance of Pt-Ni/MXene was compared with Pt/MXene, a conventional Pt/C catalyst, and found to exhibit an eight-fold enhancement in catalytic efficiency for MOR in an acidic medium.

Recent Developments in Conductive Polymer‐Based Electro‐/Photoelectrocatalytic Materials for Effective Hydrogen/Oxygen Evolution Reactions: A Review

AbstractCurrently, a substantially greener energy source such as hydrogen fuel cell is an alternative to fossil fuel sources, and much research has been dedicated to achieving highly efficient hydrogen (H2 gas) generation. In this line, electrochemical water splitting that involves hydrogen and oxygen evolution reactions (HER and OER, respectively) is considered to be the greener and most effective hydrogen‐generating procedure with only water as a by‐product. However, in the process of successful OER/HER, it is extremely demanding for electrocatalysts with high activity, stability and cost‐effectiveness for the water splitting process. Herein, the review proposed promising electrocatalysts such as conductive polymers (CPs) with enhanced catalytic effect with the polymer encapsulation of catalytic material that provides an increase in charge transfer kinetics both in OER/HER. Also, the review highlights the OER and HER mechanism of conducting polymers and their effect on the synergism was discussed in detail. Also, the review detailed the reduced overpotentials, importance and enhancement of catalytic efficiency with various polymers reported in both OER and HER. Here, the choice of polymers can matrix with the inorganic active sites to prevent them from aggregation and the water splitting carried out over the electrode surface results in good conductivity to charge transfer from the electrode to the active sites. In addition, the review discussed the polymers induces the photon effect with photoelectrocatalytic water splitting. Thus, the combing effect with conducting polymers and the materials with catalytic active centers open up a new kind of electrocatalyst for synthesis.

Stepwise synthesis of polyhedral AuAgPd nanoframes for plasmon-enhanced catalytic reduction of 4-nitrophenol

Polyhedral AuAgPd nanoframes are successfully prepared via a stepwise synthesis, exhibiting noteiceable enhancement in catalytic activity for reduction of 4-nitrophenol under UV–vis light irradiation. • AuAgPd nanoframes were prepared with a polyhedral morphology. • They showed a broad and strong absorption over the visible range. • Enhanced catalytic activity was achieved under UV–vis light irradiation. AuAgPd polyhedral nanoframes (PNFs) are prepared via stepwise synthesis and exhibit a strong and broad absorption covering the visible region. For 4-nitrophenol reduction, noticeable enhancement in catalytic efficiency is observed upon UV–vis light irradiation, confirming the structural advantages in plasmonic harvesting.

Type-II CuFe2O4/Graphitic Carbon Nitride Heterojunctions for High-Efficiency Photocatalytic and Electrocatalytic Hydrogen Generation.

Solar water splitting has emerged as an urgent imperative as hydrogen emerges as an increasingly important form of energy storage. g-C3N4 is an ideal candidate for photocatalytic water splitting as a result of the excellent alignment of its band edges with water redox potentials. To mitigate electron-hole recombination that has limited the performance of g-C3N4, we have developed a semiconductor heterostructure of g-C3N4 with CuFe2O4 nanoparticles (NPs) as a highly efficient photocatalyst. Visible-light-driven photocatalytic properties of CuFe2O4/g-C3N4 heterostructures with different CuFe2O4 loadings have been examined with two sacrificial agents. An up to 2.5-fold enhancement in catalytic efficiency is observed for CuFe2O4/g-C3N4 heterostructures over g-C3N4 nanosheets alone with the apparent quantum yield of H2 production approaching 25%. The improved photocatalytic activity of the heterostructures suggests that introducing CuFe2O4 NPs provides more active sites and reduces electron-hole recombination. The g-C3N4/CuFe2O4 heterostructures furthermore show enhanced electrocatalytic HER activity as compared to the individual components as a result of which by making heterostructures g-C3N4 with CuFe2O4 increased the active catalytic surface for the electrocatalytic water splitting reaction. The enhanced faradaic efficiency of the prepared heterostructures makes it a potential candidate for efficient hydrogen generation. Nevertheless, the designed heterostructure materials exhibited significant photo- and electrocatalytic activity toward the HER, which demonstrates a method for methodically enhancing catalytic performance by creating heterostructures with the best energetic offsets.

Engineering substrate specificity of HAD phosphatases and multienzyme systems development for the thermodynamic-driven manufacturing sugars

Naturally, haloacid dehalogenase superfamily phosphatases have been evolved with broad substrate promiscuity; however, strong specificity to a particular substrate is required for developing thermodynamically driven routes for manufacturing sugars. How to alter the intrinsic substrate promiscuity of phosphatases and fit the “one enzyme-one substrate” model remains a challenge. Herein, we report the structure-guided engineering of a phosphatase, and successfully provide variants with tailor-made preference for three widespread phosphorylated sugars, namely, glucose 6-phosphate, fructose 6-phosphate, and mannose 6-phosphate, while simultaneously enhancement in catalytic efficiency. A 12000-fold switch from unfavorite substrate to dedicated one is generated. Molecular dynamics simulations reveal the origin of improved activity and substrate specificity. Furthermore, we develop four coordinated multienzyme systems and accomplish the conversion of inexpensive sucrose and starch to fructose and mannose in excellent yield of 94–96%. This innovative sugar-biosynthesis strategy overcomes the reaction equilibrium of isomerization and provides the promise of high-yield manufacturing of other monosaccharides and polyols.

Poly(N,N-dimethylacrylamide)-stabilized gold nanoparticles as nanozymes with enhancement of catalytic activity for detection of lomefloxacin.

Recently, polymer-protected gold nanoparticles (AuNPs) have attracted extensive attention due to their good catalytic activities. However, how to regulate their catalytic activities by changing the polymer chain morphologies or the interactions between the ligands and the analytes through externalstimuli is still a great challenge. This study describes a simple synthesis of AuNPs capped by thermo-responsive poly(N,N-dimethylacrylamide) (PDMAM). In comparison with three kinds of PDMAMs@AuNPs, PDMAM-2@AuNPs exhibited better peroxidase-mimic ability via the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2) to generate oxidized TMB (oxTMB). Interestingly, its catalytic activity could be regulated by changing environmental temperature. Importantly, the addition of the antibiotic lomefloxacin endowed the PDMAM-2@AuNPs with enhancement in catalytic efficiency due to electrostatic interactions and the increased levels of reactive oxygen species. Based on this principle, a protocol for highly selective and sensitive monitoring of lomefloxacin has been constructed with the color change from pale blue to deep blue. The ultraviolet-visible absorbance of oxTMB at the wavelength of 650nm showed a good linear relationship with antibiotic concentration in the range of 0.25-10.0µM (R2 = 0.990). The limit of detection was 0.1µM. The practical application of the proposed protocol with the promoted peroxidase-mimic activity for the measurement of lomefloxacin in capsules was realized.

Cu nanoparticles-dispersed Mg-Al layered double hydroxides as efficient catalysts for CO2 conversion with propargyl alcohols

Upgrading carbon dioxide (CO2) into valuable products is a highly promising strategy of artificial carbon cycle. In this study, a series of in situ reduced CuMgAl layered double hydroxides (R-CuMgAl-LDHs) composites were synthesized, in which Cu nanoparticles were effectively dispersed and anchored on MgAl-LDHs with formation of Cu+ and Cu0 species. The optimized R-Cu1.5Mg1.5Al1-LDH exhibited excellent catalytic performance for the carboxylative cyclization of 2-methyl-3-butyn-2-ol with CO2 (turnover number of 243) under mild conditions. The layered structure of LDH stabilized the active Cu species with high dispersion, enhancing the catalytic efficiency of this carboxylative cyclization reaction. Simultaneously, the dual-activation of both CO2 and propargylic alcohol by Cu0/Cu+ species generated on the surface of LDH contributed significantly to the catalytic efficiency enhancement. Furthermore, R-Cu1.5Mg1.5Al1-LDH catalyzed the reaction of a wide range of terminal or internal propargyl alcohols with CO2, yielding various functionalized α-alkylene cyclic carbonates. Finally, a reasonable reaction mechanism was put forward according to the comprehensive analysis.

Rationally engineered chitin deacetylase from Arthrobacter sp. AW19M34-1 with improved catalytic activity toward crystalline chitin

Chitin and its derivatives have anticoagulant, antimicrobial, and antioxidant properties, but the poor solubility of chitin limits its application in different fields. In this study, site-directed mutagenesis was performed to enhance the deacetylation activity of chitin deacetylases CDA from Arthrobacter (ArCE4). The mutant Mut-2-8 with Y172E/E200S/Y201W showed a 2.84- fold and 1.39-fold increase in catalytic efficiency (kcat/Km) for the deacetylation of (GluNAc)5 and α-chitin, respectively. These results demonstrated that the mutations significantly improved the activation of ArCE4 on crystalline chitin. The molecular docking study confirmed that the enhancement of catalytic efficiency is due to the extra two hydrogen bonds and one acetyl group. In summary, the activity of Mut-2-8 to insoluble chitin was significantly improved by reactional design, which is beneficial to resolve the issues of the expensive cost of the enzymes and low efficiency. Mut-2-8 exhibits potential applications in the chitosan industry.

Dual metal nanoparticles within multicompartmentalized mesoporous organosilicas for efficient sequential hydrogenation

Controlling localization of multiple metal nanoparticles on a single support is at the cutting edge of designing cascade catalysts, but is still a scientific and technological challenge because of the lack of nanostructured materials that can not only host metal nanoparticles in different sub-compartments but also enable efficient molecular transport between different metals. Herein we report a multicompartmentalized mesoporous organosilica with spatially separated sub-compartments that are connected by short nanochannels. Such a unique structure allows co-localization of Ru and Pd nanoparticles in a nanoscale proximal fashion. The so designed cascade catalyst exhibits an order of magnitude activity enhancement in the sequential hydrogenation of nitroarenes to cyclohexylamines compared with its mono/bi-metallic counterparts. Crucially, an interesting phenomenon of neighboring metal-assisted hydrogenation via hydrogen spillover is observed, contributing to the significant enhancement in catalytic efficiency. The multicompartmentalized architectures along with the revealed mechanism of accelerated hydrogenation provide vast opportunity for designing efficient cascade catalysts.