Catalytic Platform Research Articles

Inverting glucuronidation of hymecromone in situ by catalytic nanocompartments.

Glucuronidation is a metabolic pathway that inactivates many drugs including hymecromone. Adverse effects of glucuronide metabolites include a reduction of half-life circulation times and rapid elimination from the body. Herein, we developed synthetic catalytic nanocompartments able to cleave the glucuronide moiety from the metabolized form of hymecromone in order to convert it to the active drug. By shielding enzymes from their surroundings, catalytic nanocompartments favor prolonged activity and lower immunogenicity as key aspects to improve the therapeutic solution. The catalytic nanocompartments (CNCs) consist of self-assembled poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) diblock copolymer polymersomes encapsulating β-glucuronidase. Insertion of melittin in the synthetic membrane of these polymersomes provided pores for the diffusion of the hydrophilic hymecromone-glucuronide conjugate to the compartment inside where the encapsulated β-glucuronidase catalyzed its conversion to hymecromone. Our system successfully produced hymecromone from its glucuronide conjugate in both phosphate buffered solution and cell culture medium. CNCs were non-cytotoxic when incubated with HepG2 cells. After being taken up by cells, CNCs produced the drug in situ over 24 hours. Such catalytic platforms, which locally revert a drug metabolite into its active form, open new avenues in the design of therapeutics that aim at prolonging the residence time of a drug.

CAAC-IPr*: easily accessible, highly sterically-hindered cyclic (alkyl)(amino)carbenes.

IPr* (IPr* = 1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene) has emerged as a powerful highly hindered and sterically-flexible ligand platform for transition-metal catalysis. CAACs (CAAC = cyclic (al-kyl)(amino)carbenes) have gained major attention as strongly electron-rich carbon analogues of NHCs (NHC = N-heterocyclic carbene) with broad applications in both industry and academia. Herein, we report a merger of CAAC ligands with highly-hindered IPr*. The efficient synthesis, electronic characterization and application in model Cu-catalyzed hydroboration of alkynes is described. The ligands are strongly electron-rich, bulky and flexible around the N-Ar wingtip. The availability of various IPr* and CAAC templates offers a significant potential to expand the existing arsenal of NHC ligands to electron-rich bulky architectures with critical applications in metal stabilization and catalysis.

Poss-Al-Porphyrin-Imidazolium Cross-Linked Network as Catalytic Bifunctional Platform for the Conversion of Co2 with Epoxides

Poss-Al-Porphyrin-Imidazolium Cross-Linked Network as Catalytic Bifunctional Platform for the Conversion of Co2 with Epoxides

Hairpin-functionalized DNA tetrahedra for miRNA imaging in living cells via self-assembly to form dendrimers.

DNA self-assembling nanoprobes with self-transferability and resistance to nuclease degradation have been developed and applied to live cell bio-imaging. In this work, we constructed a hairpin-functionalized DNA tetrahedron (HFDT) intramolecular catalytic self-assembly platform to detect low-abundance miRNAs by a catalyzed hairpin assembly (CHA). The designed HFDT enhances the CHA reaction efficiency and aggregates into dendrimer structures in the presence of miRNAs. This innovative "small to large" strategy can effectively change the distribution and properties of biomaterials in the organism, thus effectively retaining them inside the tumor and reducing the efflux of nanomaterials, increasing their accumulation in the tumor site and protecting them from the complex physiological environment, which has promising applications in tumor imaging.

Perovskite photocatalysis: realizing long-lived charge-separated states at the interface of CsPbBr3nanocrystals and functionalized ferrocene molecules

We have shown strong coupling-guided interfacial hole transfer dynamics between CsPbBr3perovskite NCs and functionalized ferrocene derivatives. We could achieve a long-lived charge-separated state, which provides an ideal platform for catalysis.

Copper ferrite nanoparticles loaded on reduced graphene oxide nanozymes for the ultrasensitive colorimetric assay of chromium ions.

Nowadays, due to the increasing threat of heavy metal ion pollution faced by the environment and living systems, the development of rapid and highly selective methods for the detection of chromium ions (Cr3+) has aroused increasing interest. In this study, copper ferrite nanoparticles (CuFe2O4) immobilized on reduced graphene oxide (CuFe2O4/rGO) were successfully fabricated by a simple co-precipitation method. The catalyst exhibits high peroxidase-like activity with 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic matrix due to its large specific surface area, adsorption performance and abundant catalytic active sites. Based on the excellent peroxidase-like activity of CuFe2O4/rGO and its Cr3+-mediated inhibition controllability, a novel colorimetric assay for the heavy metal Cr3+ was created for the first time. Under optimal experimental conditions, CuFe2O4/rGO can be used as a peroxidase-like nanozyme to achieve the excellent detection of Cr3+ in the range of 0.1-25 μM, and the detection limit is 35 nM. The peroxidase-like CuFe2O4/rGO can provide a general catalytic platform for the application of biomimetic enzymatic catalytic systems and colorimetry, and a new approach has been established for the specific determination of the heavy metal Cr3+.

Ladder-Like DNA Nanostructure-Mediated Cascade Catalytic Nanomachine for Construction of Ultrasensitive Biosensors.

Herein, a novel two-dimensional ladder-like DNA nanostructure (LDN)-mediated cascade catalytic nanomachine (LDN-CCN) with a higher catalytic efficiency beyond those of a conventional one-dimensional hybrid chain reaction (HCR) nanostructure-mediated CCN was constructed and applied to design an electrochemical biosensing platform with first-rank performance for ultrasensitive detection of target miRNA-21. First, output DNA S1' and S2' were produced through the DNAzyme recycle amplification when the target miRNA-21 existed. Then, the controllable LDN-CCN was constructed on S1-S2 modified electrodes by the subsequent reaction triggered by S1' and S2' with H1-AuNPs, H2, H3-AuNPs, and H4 with the assistance of K+ and hemin, in which the hemin/G-quadruplexes could produce a prominent electrochemical signal response to the substrate glucose. The best performance of cascade catalysis was acquired when the distance of Au nanoparticles (glucose oxidase-like activity) modified on H1 and H3 and hemin/G-quadruplexes (peroxidase-like activity) formed by the sticky ends of H2 and H4 was roughly 9 nm (27 bp) in LDN-CCN. The constructed electrochemical platform realized the sensitive detection of target miRNA-21 with the linear range from 100 aM to 10 nM and with a detection limit as low as 48.5 aM, which provided novel insights to explore the new functional DNA nanostructure and well-performing mimic enzyme cascade catalytic platforms for applications in biological fields and early diagnosis of diseases.

Creating Dynamic Nanospaces in Solution by Cationic Cages as Multirole Catalytic Platform for Unconventional C(sp)−H Activation Beyond Enzyme Mimics

AbstractHerein we demonstrate that, based on the creation of dynamic nanospaces in solution by highly charged positive coordination cage of [Pd6(RuL3)8]28+, multirole and multi‐way cage‐confined catalysis is accomplishable for versatile functions and anomalous reactivities with the aid of the biomimetic cage effect. The high cationic‐host charges drive partial deprotonation of 24 imidazole‐NHs on cage sphere alike imidazole‐residuals in proteins, generating amphoteric heterogeneity in solution to enforce effective cavity‐basicity against solution‐acidity. Synergistic actions arisen from cage hydrophobicity, host‐guest electrostatic interactions and imidazole‐N coordination facilitate C(sp)−H activation and carbanionic intermediate stabilization of terminal alkynes to achieve unusual H/D‐exchange and Glaser coupling under acidic conditions, and enable phase transfers of water‐insoluble substrates/products/co‐catalysts to make immiscible‐phase and bi‐phase catalysis feasible, thus providing a useful catalytic protocol to combine merits from homogeneous, heterogeneous, enzymatic and phase transfer catalysis.

Creating Dynamic Nanospaces in Solution by Cationic Cages as Multirole Catalytic Platform for Unconventional C(sp)-H Activation Beyond Enzyme Mimics.

Herein we demonstrate that, based on the creation of dynamic nanospaces in solution by highly charged positive coordination cage of [Pd6 (RuL3 )8 ]28+ , multirole and multi-way cage-confined catalysis is accomplishable for versatile functions and anomalous reactivities with the aid of the biomimetic cage effect. The high cationic-host charges drive partial deprotonation of 24 imidazole-NHs on cage sphere alike imidazole-residuals in proteins, generating amphoteric heterogeneity in solution to enforce effective cavity-basicity against solution-acidity. Synergistic actions arisen from cage hydrophobicity, host-guest electrostatic interactions and imidazole-N coordination facilitate C(sp)-H activation and carbanionic intermediate stabilization of terminal alkynes to achieve unusual H/D-exchange and Glaser coupling under acidic conditions, and enable phase transfers of water-insoluble substrates/products/co-catalysts to make immiscible-phase and bi-phase catalysis feasible, thus providing a useful catalytic protocol to combine merits from homogeneous, heterogeneous, enzymatic and phase transfer catalysis.

Metallaphotoredox: The Merger of Photoredox and Transition Metal Catalysis.

The merger of photoredox catalysis with transition metal catalysis, termed metallaphotoredox catalysis, has become a mainstay in synthetic methodology over the past decade. Metallaphotoredox catalysis has combined the unparalleled capacity of transition metal catalysis for bond formation with the broad utility of photoinduced electron- and energy-transfer processes. Photocatalytic substrate activation has allowed the engagement of simple starting materials in metal-mediated bond-forming processes. Moreover, electron or energy transfer directly with key organometallic intermediates has provided novel activation modes entirely complementary to traditional catalytic platforms. This Review details and contextualizes the advancements in molecule construction brought forth by metallaphotocatalysis.

Single-Atom Engineering to Ignite 2D Transition Metal Dichalcogenide Based Catalysis: Fundamentals, Progress, and Beyond.

Single-atom catalysis has been recognized as a pivotal milestone in the development history of heterogeneous catalysis by virtue of its superior catalytic performance, ultrahigh atomic utilization, and well-defined structure. Beyond single-atom protrusions, two more motifs of single-atom substitutions and single-atom vacancies along with synergistic single-atom motif assemblies have been progressively developed to enrich the single-atom family. On the other hand, besides traditional carbon material based substrates, a wide variety of 2D transitional metal dichalcogenides (TMDs) have been emerging as a promising platform for single-atom catalysis owing to their diverse elemental compositions, variable crystal structures, flexible electronic structures, and intrinsic activities toward many catalytic reactions. Such substantial expansion of both single-atom motifs and substrates provides an enriched toolbox to further optimize the geometric and electronic structures for pushing the performance limit. Concomitantly, higher requirements have been put forward for synthetic and characterization techniques with related technical bottlenecks being continuously conquered. Furthermore, this burgeoning single-atom catalyst (SAC) system has triggered serial scientific issues about their changeable single atom-2D substrate interaction, ambiguous synergistic effects of various atomic assemblies, as well as dynamic structure-performance correlations, all of which necessitate further clarification and comprehensive summary. In this context, this Review aims to summarize and critically discuss the single-atom engineering development in the whole field of 2D TMD based catalysis covering their evolution history, synthetic methodologies, characterization techniques, catalytic applications, and dynamic structure-performance correlations. In situ characterization techniques are highlighted regarding their critical roles in real-time detection of SAC reconstruction and reaction pathway evolution, thus shedding light on lifetime dynamic structure-performance correlations which lay a solid theoretical foundation for the whole catalytic field, especially for SACs.

A Nickel/Photoredox Dual Catalytic Platform for Late-Stage Functionalization of N-Me Trialkylamines

Key words nickel catalysis - photoredox catalysis - late-stage functionalization - arylation

Metal Organic Frameworks as Heterogeneous Catalysts in Olefin Epoxidation and Carbon Dioxide Cycloaddition

Metal–organic frameworks (MOFs) are a family of porous crystalline materials that serve in some cases as versatile platforms for catalysis. In this review, we overview the recent developments about the use of these species as heterogeneous catalysts in olefin epoxidation and carbon dioxide cycloaddition. We report the most important results obtained in this field relating them to the presence of specific organic linkers, metal nodes or clusters and mixed-metal species. Recent advances obtained with MOF nanocomposites were also described. Finally we compare the results and summarize the major insights in specific Tables, outlining the major challenges for this emerging field. This work could promote new research aimed at producing coordination polymers and MOFs able to catalyse a broader range of CO2 consuming reactions.

A facile nanozyme based catalytic platform for the selective and sensitive detection of thrombin

Herein, a label-free and ultra-sensitive sensing strategy was proposed for the colorimetric detection of thrombin. A catechol oxidase-mimicking nanozyme, MOF-818, was in-situ uniformly synthesized on carbon cloth (CC) fibers surface by hydrothermal method, which did not aggregate during the colorimetric sensing and showed high catalytic activity to the oxidation of faint yellow colored substrate 3,5-Di-tert-butylcatechol (3,5-DTBC) to luminous yellow colored 3,5-di-tert-butyl-obenzoquinone (3,5-DTBQ). After the conjugation of aptamer on MOF-818/CC, the nanozyme composite can effectively recognize and bind thrombin, resulting in the lighter color of substrate solution and the decrease of absorbance at 414 nm. Thus, the inhibition of the nanozyme activity by the bound thrombin was employed to detect thrombin in a wide linear range and a low limit of detection of 1.4 × 10−10M − 1.4 × 10−5M and 6.4 pM, respectively, which was superior to the most of reported methods including fluorescence and electrochemical sensing, Raman spectroscopy. Meanwhile, the nanozyme composite can be easily separated from the substrate solution by a tweezers instead of the conventional centrifugation, which greatly simplified the operation process and facilitated the on-site detection. The nanozyme composite has been successfully applied for the determination of thrombin in real samples with satisfactory results. Consequently, this work is not only important for a better understanding of the unique properties of MOF-818, but also has great potential for medical diagnosis and treatment of human health.

Photoredox-Catalyzed Synthesis of Remote Fluoroalkylated Azaarene Derivatives and the α-Deuterated Analogues via 1,n-Hydrogen-Atom-Transfer-Involving Radical Reactions.

A modular strategy to access the remote fluoroalkylated azaarene derivatives and the α-deuterated analogues, which are the isosteres of many pharmaceutically important compounds, is reported. Transformations under the sustainable photoredox catalysis platform could efficiently experience cascade radical addition, 1,n-hydrogen atom transfer (HAT), and single-electron reduction to offer the crucial anions α to azaarenes. Through reacting with H2O or the inexpensive D2O, two series of valuable products were obtained in high yields with substantial deuterium incorporation. The work demonstrates that the HAT of the α-sp3 C-H of the electron-withdrawing azaarenes with alkyl radicals is viable.

Nanocarbons in quantum regime: An emerging sustainable catalytic platform for organic synthesis

ABSTRACT Fluorescent carbon quantum dots (CQDs), specified by feature sizes of <10 nm, have become a mystic newcomers in the world of nanoscience and attracted much focus of synthetic chemists since the last decade due to their esoteric physico-chemical features. Because of these magical characteristics, carbon dots-based catalytic systems have unlocked the gateway for eco-friendly, benign, and cost-effective next-generation platform for “Nanocatalysis and Photocatalysis” in organic synthesis. The introduction of CQDs in organic synthesis allows the designing new reactions or catalysis in which unique/unprecedented connection/disconnection of chemical bonds has been implemented for the construction of new molecular architectures. This critical review presents a comprehensive study of the catalytic and photocatalytic efficiency of CQDs in organic synthesis which has initiated a more sustainable strategy in to the catalysis field. By systematic summarization and categorization of various organic transformations such as coupling reactions, oxidation reactions, reduction reactions, condensation reactions, ring-opening reactions, epoxidation, C-H activation, etc., a clear picture of all available catalytic and photocatalytic strategies for CQDs are presented and their unique role in various catalytic approaches for specific reactions are discussed in detail. Catalytic aspects of CQDs in heterocyclic synthesis are also been reviewed. Finally, challenges and future aspects associated with the green catalytic efficiency of CQDs in organic synthesis are highlighted. Herein, this review summarizes the current investigations on CQDs for various organic transformations during last 10 years. We experience that the entire potential of CQDs in organic synthesis has yet to be fully explored in organic synthesis. We hope that this review is serving as a humble urge to encourage other organic chemists for further use of CQDs as a sustainable catalyst in organic synthesis.

Single‐chain polymers as homogeneous oxidative photoredox catalysts

AbstractSingle‐chain polymer nanoparticles (SCNPs) are emerging as versatile catalytic platforms that provide excellent control over solubility. The confined nature of SCNPs can improve the rate of catalysis. While significant headway has been made in thermally‐induced transition‐metal catalysis with SCNPs, light‐activated SCNP catalysts have received little attention. We are developing triarylpyrylium tetrafluoroborate (TPT)‐functionalized SCNPs as oxidative photocatalysts. Herein, we comprehensively study the impact of light source on both SCNP compaction and TPT absorbance through gel‐permeation chromatography and UV/Vis spectroscopy. We observe that compaction is expedited using light sources that excite the photocatalyst (e.g., blue LEDs), which is attributed to the ability of TPT to dimerize sytrenics under similar photoredox conditions. The resultant metal‐free SCNP photocatalysts enable the oxidation of benzyl alcohols in good yields. The SCNP is further investigated for the amidation of 4‐bromobenzaldehyde, wherein it affords higher yields of the benzamide product compared to both small‐molecule and unfolded polymer controls. We attribute the combined results to the colocalization of the TPT photoredox catalyst and pyrene electron relay within the SCNP, which likely aids in single‐electron transfer processes. The scope of amidation reactions was also extended to other aryl aldehydes, wherein deactivated substrates afforded the highest yield of the desired amide.

Tuning the catalytic activity of enzymes embedded in layer-by-layer assembled films

Immobilization of enzymes on supporting materials for biocatalysis is highly desired for industrial applications, because it endows the biocatalytic platform with significant advantages compared to free enzymes, e.g., easy separation, re-usability, and long-term stability. However, the possible denaturation of immobilized enzymes by the underlying substrate or crosslinking, and the limited amount of attached enzymes, often results in a low enzymatic activity. Here, we employ polyelectrolytes to assemble glucose oxidase in thick films in a layer-by-layer (LbL) way. By screening a large range of conditions, we show that the immobilized enzymes may retain their intrinsic structure and display a high activity when deposited in suitable conditions with the appropriate polycation. Moreover, the activity of formed multilayer enzyme films can be tuned depending on deposition conditions. We also demonstrate swelling of the film by the reaction medium by in-situ AFM measurements, with the film behaving as a hydrogel in which the enzymatic substrate can easily access the active site of enzymes immobilized all along the film. Hence, despite the complexity of protein adsorption in LbL films, conditions for stable growth of active enzymatic films of tunable activity can be found, offering a promising way to design highly active enzyme-immobilized catalytic platforms.

Microwave-Assisted Electrostatically Enhanced Phenol-Catalyzed Synthesis of Oxazolidinones.

An electrostatically enhanced phenol is utilized as a straightforward, sustainable, and potent one-component organocatalyst for the atom-economic transformation of epoxides to oxazolidinones under microwave irradiation. Integrating a positively charged center into phenols over a modular one-step preparation gives rise to a bifunctional system with improved acidity and activity, competent in rapid assembly of epoxides and isocyanates under microwave irradiation in a short reaction time (20-60 min). A careful assessment of the efficacy of various positively charged phenols and anilines and the impact of several factors, such as catalyst loading, temperature, and the kind of nucleophile, on catalytic reactivity were examined. Under neat conditions, this one-component catalytic platform was exploited to prepare more than 40 examples of oxazolidinones from a variety of aryl- and alkyl-substituted epoxides and isocyanates within minutes, where up to 96% yield and high degree of selectivity were attained. DFT calculations to achieve reaction barriers for different catalytic routes were conducted to provide mechanistic understanding and corroborated the experimental findings in which concurrent epoxide ring-opening and isocyanate incorporation were proposed.

Graphene‐Based Nanomaterials for Biomedical, Catalytic, and Energy Applications

AbstractNanotechnology has provided us with unimaginable possibilities in addressing worldly challenges. Since its discovery in 2004, Graphene has been considered a “Holy Grail” of nanomaterials for its unprecedented applicability in different fields, including biomedical, energy harvest and storage, sensing applications. Throughout the world, tremendous waves of research have been going on to exploit graphene‘s unique thermal, mechanical, electrical, catalytic, and biological properties. Besides, efficient and tunable techniques of graphene‘s bulk manufacturing have been under thorough investigation. This article reviews various recent studies on large‐scale graphene synthesis with tunable properties. Several different ways of graphene‘s use in various catalytic platforms are also reviewed. Furthermore, recent biomedical and energy (storage and harvest) applications of graphene, especially in microbial fuel cell technology, bio‐sensing, antimicrobial applications, have been discussed in this article.