An efficient mimic of cytochrome P-450 from a zeolite-encaged iron complex in a polymer membrane

Spatial engineering of single-atom Fe adjacent to Cu-assisted nanozymes for biomimetic O2 activation

The precise design of single-atom nanozymes (SAzymes) and understanding of their biocatalytic mechanisms hold great promise for developing ideal bio-enzyme substitutes. While considerable efforts have been directed towards mimicking partial bio-inspired structures, the integration of heterogeneous SAzymes configurations and homogeneous enzyme-like mechanism remains an enormous challenge. Here, we show a spatial engineering strategy to fabricate dual-sites SAzymes with atomic Fe active center and adjacent Cu sites. Compared to planar Fe-Cu dual-atomic sites, vertically stacked Fe-Cu geometry in FePc@2D-Cu-N-C possesses highly optimized scaffolds, favorable substrate affinity, and fast electron transfer. These characteristics of FePc@2D-Cu-N-C SAzyme induces biomimetic O2 activation through homogenous enzymatic pathway, resembling functional and mechanistic similarity to natural cytochrome c oxidase. Furthermore, it presents an appealing alternative of cytochrome P450 3A4 for drug metabolism and drug-drug interaction. These findings are expected to deepen the fundamental understanding of atomic-level design in next-generation bio-inspired nanozymes.

Zeolite encapsulated organometallic complexes as model catalysts

Heterogeneities in the structure of active centers in metal-containing porous materials are unavoidable and complicate the description of chemical events occurring along reaction coordinates at the atomic level. Metal containing zeolites include sites of varied local coordination and secondary confining environments, requiring careful titration protocols to quantify the predominant active sites. Hybrid organometallic-zeolite catalysts are useful well-defined platform materials for spectroscopic, kinetic, and computational studies of heterogeneous catalysis that avoid the complications of conventional metal-containing porous materials. Such materials have been synthesized and studied previously, but catalytic applications were mostly limited to liquid-phase oxidation and electrochemical reactions. The hydrothermal stability, time-on-stream stability, and utility of these materials in gas-phase oxidation reactions are under-studied. The potential applications for single-site heterogeneous catalysts in fundamental research are abundant and motivate future synthetic, spectroscopic, kinetic, and computational studies.

Mn(III) Schiff base complexes containing crown ether rings immobilized onto MCM-41 matrix as heterogeneous catalysts for oxidation of alkenes

Six catalysts MnL¹-MnL⁶, containing two crown ether rings and their analogs supported on the MCM-41 heterogeneous substrate (MnL¹@MCM41-MnL⁵@MCM41) were synthesized and characterized. A mixture of molecular oxygen, as an oxidant, and these catalysts were used for the epoxidation of styrene. As a general result, the supported catalysts showed better performance compared with the unsupported analogs. On the other hand, the supported species, in addition to recyclability, did not require an axial base and reducing agent.

Exploration of nanozymes in viral diagnosis and therapy

Nanozymes are nanomaterials with similar catalytic activities to natural enzymes. Compared with natural enzymes, they have numerous advantages, including higher physiochemical stability, versatility, and suitability for mass production. In the past decade, the synthesis of nanozymes and their catalytic mechanisms have advanced beyond the simple replacement of natural enzymes, allowing for fascinating applications in various fields such as biosensing and disease treatment. In particular, the exploration of nanozymes as powerful toolkits in diagnostic viral testing and antiviral therapy has attracted growing attention. It can address the great challenges faced by current natural enzyme-based viral testing technologies, such as high cost and storage difficulties. Therefore, nanozyme can provide a novel nanozyme-based antiviral therapeutic regime with broader availability and generalizability that are keys to fighting a pandemic such as COVID-19. Herein, we provide a timely review of the state-of-the-art nanozymes regarding their catalytic activities, as well as a focused discussion on recent research into the use of nanozymes in viral testing and therapy. The remaining challenges and future perspectives will also be outlined. Ultimately, this review will inform readers of the current knowledge of nanozymes and inspire more innovative studies to push forward the frontier of this field.

Ronald C.D. Breslow (1931-2017): A career in review

Reviewed herein are key research accomplishments of Professor Ronald Charles D. Breslow (1931-2017) throughout his more than 60 year research career. These accomplishments span a wide range of topics, most notably physical organic chemistry, medicinal chemistry, and bioorganic chemistry. These topics are reviewed, as are topics of molecular electronics and origin of chirality, which combine to make up the bulk of this review. Also reviewed briefly are Breslow's contributions to the broader chemistry profession, including his work for the American Chemical Society and his work promoting gender equity. Throughout the article, efforts are made to put Breslow's accomplishments in the context of other work being done at the time, as well as to include subsequent iterations and elaborations of the research.

Zeolite-Y encapsulated cobalt(ii) Schiff-base complexes employed for photocatalytic dye-degradation and upcycling CO2

Planar cobalt(ii) Schiff-base complexes show modified structural and functional properties after encapsulation inside zeolite-Y.

Effect of porphyrin metal center on synthesis, structure, morphology and oxygen reduction properties of porphyrin encapsulated metal organic frameworks

A series of different metal centered 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl)porphyrins (PorM) where M = H2, MnOAc, FeCl, Co or Zn were synthesized, and then encapsulated in zeolite imidazole framework-8 (ZIF-8) by typical template directed strategy to generate PorM@ZIF-8 metal organic frameworks (MOFs). These composites were characterized by UV-vis, FTIR, XRD, FESEM and HRTEM methods. Each prepared PorM@ZIF-8 MOF retained the molecular structure of porphyrin and crystal structure of ZIF-8. It is clearly shown that porphyrin centered metal ions will affect MOFs morphology. Both PorH2@ZIF-8 and PorZn@ZIF-8 gave a rhombic dodecahedron, PorMnOAc@ZIF-8 gave a truncated hexagonal prism-like structure, while no specific structures were obtained for PorFeCl@ZIF-8 and PorCo@ZIF-8 due to aggregation as characterized by FESEM spectrum. Oxygen reduction catalytic ability of ZIF-8, PorM and PorM@ZIF-8 were measured in alkaline condition (0.1 M KOH) with the number of electrons transferred being [Formula: see text] = 2.20–2.60 and generating HO[Formula: see text] as the oxygen reduction product. The catalytic property slightly increased after the porphyrin was encapsulated, due possibly to the capacity limit, inappropriate molecular distance or the direction of encapsulated porphyrin molecular.

Recent advances in metalloporphyrins for environmental and energy applications

Porphyrin-based chemistry has reached an unprecedented period of rapid development after decades of study. Due to attractive multifunctional properties, porphyrins and their analogues have emerged as multifunctional organometals for environmental and energy purposes. In particular, pioneer works have been conducted to explore their application in pollution abatement, energy conversion and storage and molecule recognition. This review summarizes recent advances of porphyrins chemistry, focusing on elucidating the nature of catalytic process. The Fenton-like redox chemistry and photo-excitability of porphyrins and their analogues are discussed, highlighting the generation of high-valent iron oxo porphyrin species. Finally, challenges in current research are identified and perspectives for future development in this area are presented.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Comparative study of the crowding-induced collapse effect in hard-sphere, flexible polymer and rod-like polymer systems

A systematic Langevin simulation is performed to study the crowding-induced collapse effect on a probed chain in three typical systems: hard sphere (HS), flexible polymer and rod-like polymer.

Coordinative integration of copper (II) and iron (II) phthalocyanine into amidoximated PAN fiber for enhanced photocatalytic activity under visible light irradiation

Metal phthalocyanine (MPc) complexes hold great promise for photocatalysis applications because of their high visible light harvesting efficiency and semiconductive properties. However, the effective development requires the suppression of their rapid charge recombination. Transition metal ions can act as electron traps to enhance the charge separation of semiconductors, but challenges still remain for bimetallic co-catalysis of MPc due to the difficulties in the combination between them. Herein, we proposed a new approach to enable the assisted metal ions to interact with MPc through fibrous support, constructing a novel bimetallic photocatalyst via simultaneously immobilizing iron(II) phthalocyanine (FePc) and Cu(II) onto the surface of amidoximated polyacrylonitrile (PAN) fiber. Taking the photodegradation of organic dyes as model reactions, this bimetallic catalyst achieves much higher photoactivity than that of the monometallic FePc catalyst, and effectively converts surface H₂O₂ into hydroxyl radicals rather than superoxide radicals and high-valent metal-oxo species. The Cu(II) not only enables the transfer of photoexcited electrons from FePc, but also promotes the running of Fe(II)/Fe(III) cycle to boost reactive radicals generation through H₂O₂ activation. The strategy of coupling Cu(II) with MPc through fibrous support provides a facile and promising solution for the advancement of MPc-based photocatalysis via visible light energy.

Enhanced catalytic activity and magnetization of encapsulated nickel Schiff-base complexes in zeolite-Y: a correlation with the adopted non-planar geometry

Square planar Ni(ii)-Schiff base complexes when encapsulated in a supercage of zeolite Y have shown altered optical and magnetic properties and catalytic activities in comparison to their corresponding free states.

Encapsulation of a Ni salen complex in zeolite Y: an experimental and DFT study

A planar diamagnetic Ni-complex when encapsulated in zeolite Y adopts a nonplanar geometry and shows a pragmatic change in its magnetic properties.

Synthesis and catalytic properties of a novel phthalocyanine covalently grafted onto silica

The iron complex of 2(3),9(10),16(17),23(24)-tetra[1,5-di(3-triethoxysilyl-propyl)biuryl]phthalocyanine (1) was prepared by reacting iron tetraaminophthalocyanine with 3-(triethoxysilyl)propyl isocyanate. This complex was directly grafted onto silica to give a supported catalyst without preliminary modification of silica support. This supported catalyst was successfully applied in clean catalytic oxidations by using molecular oxygen in combination with isobutyraldehyde. Cyclooctene, cyclohexene and styrene were oxidized to corresponding epoxides with 90, 78 and 74% yields, respectively. 2,3,6-Trimethylphenol was selectively oxidized to 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol.

Epoxidation of alkenes catalyzed by phenyl group-modified, periodic mesoporous organosilica-entrapped, dimeric manganese-salen complexes

A series of reusable, recoverable, diamine-bridged dimeric manganese-salen complexes were prepared by the encapsulation of homogeneous dimeric Mn(salen) complexes into nanocages of a 3D periodic mesoporous organosilica (PMO) support followed by silylation of the support with organosilane. The composition, structure, morphology, and textural properties of the prepared PMO-entrapped dimeric Mn(salen) complexes were characterized, and their catalytic performances were tested in the epoxidation of alkenes (styrene, cyclohexene, and 1-phenylcyclohexene), with NaClO as an oxygen source and 4-phenylpyridine-N-oxide as an axial ligand. Furthermore, the influences of the textural and morphological properties of the entrapped dimeric Mn(salen) complexes and the key reaction parameters on the catalytic activity and selectivity are discussed. Finally, the reusability of the supported dimeric Mn(salen) complexes was evaluated over three catalytic runs.

Cu-ZSM-5: A biomimetic inorganic model for methane oxidation

The present work highlights recent advances in elucidating the methane oxidation mechanism of inorganic Cu-ZSM-5 biomimic and in identifying the reactive intermediates that are involved. Such molecular understanding is important in view of upgrading abundantly available methane, but also to comprehend the working mechanism of genuine Cu-containing oxidation enzymes.

Molecular Sieve Synthesis using Metallocenes as Structure Directing Agents

We have been exploring molecular sieve synthesis using metal complexes as templates. Our objectives were to affect the crystallization of new structures as well as prepare bifunctional catalysts via the encapsulation of metal complexes during synthesis. In this paper the results for the synthesis of SiO2, AlPO4 and SAPO molecular sieves in the presence of metallocenes will be presented. In particular, Cobalticinium ion, Cp2Co+, was found to be a template for Nonasil, AlPO4−5, AlPO4−16, SAPO−16 and CoAPO−16 which are known phases but require templates. The larger decamethyl derivative, CP*2Co+ has produced a novel high silica zeolite molecular sieve, UTD-1 as well as a new SAPO phase UTD-2 which appear to be large pore materials. In all cases, the metal complex is occluded intact and cannot be extracted. Aspects of the synthesis and characterization of these microporous materials are presented below.