We present the precise synthesis of Cu,Fe DACs supported on UiO-66-NH 2 . The DACs show high selectivity towards benzaldehyde in photocatalytic styrene oxidation by efficient O 2 activation.

The large-scale synthesis of supported multinuclear catalysts with controllable metal nuclearity and constituent composition remains a formidable challenge. We report the stepwise assembly of supported atom-precise bimetallic ligand-mediated metal ensembles (LMMEs) by exploiting the underlying principles of coordination chemistry and solid-state chemistry. Lewis di-basic 2-methylimidazole is used to bridge multiple Cu2+ and M2+ (M = Co, Ni, Cu, and Zn) ions within ZSM-5 zeolites. We observe the metal constituent composition of the LMMEs by mass spectroscopy. The adjacent metal nuclei in the LMMEs offer substantial synergistic effects that enhance the catalytic performance by at least an order of magnitude in the model catalytic "click "reaction. It is envisaged that this stepwise assembly approach to develop supported multinuclear catalysts with atom precision could effectively bridge homogeneous and heterogeneous catalysis.

Precisely tuning the nuclearity of supported metal nanoclusters is pivotal for designing more superior catalytic systems, but it remains practically challenging. By utilising the chemical and molecular specificity of UiO-66-NH2 (a Zr-based metal-organic framework), we report the controlled synthesis of supported bi- and trinuclear Cu-oxo nanoclusters on the Zr6O4 nodal centres of UiO-66-NH2. We revealed the interplay between the surface structures of the active sites, adsorption configurations, catalytic reactivities and associated reaction energetics of structurally related Cu-based 'single atoms' and bi- and trinuclear species over our model photocatalytic formic acid reforming reaction. This work will offer practical insight that fills the critical knowledge gap in the design and engineering of new-generation atomic and nanocluster catalysts. The precise control of the structure and surface sensitivities is important as it can effectively lead to more reactive and selective catalytic systems. The supported bi- and trinuclear Cu-oxo nanoclusters exhibit notably different catalytic properties compared with the mononuclear 'Cu1' analogue, which provides critical insight for the engineering of more superior catalytic systems.

Fe-N-C materials, when prepared as single-atom catalysts (SAC), display excellent activities in oxidation reactions. The systematic investigation of the iron coordination mode revealed that Fe-N4C catalysts are the most active for C-H bond oxidation. However, many of these catalysts are synthesized through pyrolysis, which is characterized by a lack of control and structures with heterogeneous composition, rarely presenting only atomically dispersed Fe-N-C as active sites. Herein, an alternative, reliable and easily reproducible method to obtain highly active Fe SACs (atomically dispersed) with Fe-N4 sites is presented, which is based on ion exchange of sodium from high crystalline sodium poly(heptazine imide) (Na-PHI) by other ions. The obtained catalyst can photocatalytically oxidize C-H bonds selectively toward ketones using only dioxygen. Detailed mechanism investigations indicate that the active species in the C-H bond oxidation are highly valent Fe(IV)/Fe(V)-oxo species, which are further activated by the holes generated at the PHI support under light irradiation.

In this work, a simple one-step thermal oxidation process was established to achieve a significant surface increase in {110} and {111} nanofacets on well-defined, pure and Pr-doped, ceria nanocubes. More importantly, without changing most of the bulk properties, this treatment leads to a remarkable boost of their enzymatic activities: from the oxidant (oxidase-like) to antioxidant (hydroxyl radical scavenging) as well as the paraoxon degradation (phosphatase-like) activities. Such performance improvement might be due to the thermally generated sawtoothlike {111} nanofacets and defects, which facilitate the oxygen mobility and the formation of oxygen vacancies on the surface. Finally, possible mechanisms of nanoceria as artificial enzymes have been proposed in this manuscript. Considering the potential application of ceria as artificial enzymes, this thermal treatment may enable the future design of highly efficient nanozymes without changing the bulk composition.

We report the guest-anion-induced photoluminescence enhancement of metalorganic frameworks (UiO-66-NH2), first based upon diffraction and computational evidence. We found that only limited anions, namely, carbonate and fluoride, can lead to a significant enhancement in photoluminescence, whereas their related anions, such as acetate and chloride, cannot. The optimized crystal structures reveal that the guest carbonate and fluoride ions interact with four framework amino functional groups through hydrogen bonding (ca. 1.6-1.7 angstrom) that ultimately forms a quaternary (-N(H))(4)...X- molecular bridge around the nodal center. Hence, the hydrogen-bonded molecular bridge not only restricts the intermolecular C-C rotation of the linker molecules but also greatly perturbs the electronic densities between the guest anions and the framework amino groups.

This minireview highlights some recent advances in the rational design of precise Cu nanoclusters supported on microporous materials, including zeolites and metal-organic frameworks. The development of comprehensive characterisation techniques enables scientists to elucidate the structure-activity relationship of these catalysts, which aids the subsequent engineering of more superior catalytic systems at an atomistic perspective.

We investigate the geometric and electronic properties of single-atom catalysts (SACs) within metal-organic frameworks (MOFs) with respect to electrocatalytic CO2 reduction as a model reaction. A series of mid-to-late 3d transition metals have been immobilised within the microporous cavity of UiO-66-NH2. By employing Rietveld refinement of new-generation synchrotron diffraction, we not only identified the crystallographic and atomic parameters of the SACs that are stabilised with a robust MN(MOF) bonding of ca. 2.0 Å, but also elucidated the end-on coordination geometry with CO2. A volcano trend in the FEs of CO has been observed. In particular, the confinement effect within the rigid MOF can greatly facilitate redox hopping between the Cu SACs, rendering high FEs of CH4 and C2H4 at a current density of -100 mA cm-2. Although only demonstrated in selected SACs within UiO-66-NH2, this study sheds light on the rational engineering of molecular interactions(s) with SACs for the sustainable provision of fine chemicals.

A novel non-enzyme electrochemical sensor was constructed based on nanoceria and gold nanoparticle for non-invasive glucose monitoring.

One of the commonly used tool in enhance oil recovery (EOR) is nitrogen foam flooding. The sweeping efficiency is largely determined by the foam stability. Recently the study on using nanoparticle, alone or with other chemicals, to stabilize foam has emerged in several fields of foam application. In this study, we use a combination of physicochemical tools to analyze the synergetic effect of ionic liquid cetylpyridinium chloride (CPC) with nanoparticle in foam flooding of EOR. Two different nanoparticles (NPs), one hydrophilic and the other hydrophobic, are compared in terms of sweeping efficiency. It was found that CPC with hydrophilic NPs is much more effective in foam flooding residue oil than with hydrophobic NPs. This may be due to the difference in CPC orientation on NP surfaces, thus affecting the surface properties including surface tension, elasticity and contact angle. Consequently the stability of foam, which underpins the oil displacement efficiency in EOR, is influenced. The possible interaction and mechanism between CPC, NP and oil are discussed while considering the contribution from reduction of drainage rate, higher particle adsorption energy, and higher surface elasticity. Understanding the differential roles of hydrophilic and hydrophobic nanoparticles in ionic liquid stabilized foam as well as physical mechanism underpinning their specificity could help facilitate the development of new green nanomaterial in the application of EOR.

Ceria nanocubes (NC) modified with increasing concentrations of praseodymium (5, 10, 15, and 20 mol %) have been successfully synthesized by a hydrothermal method. The as-synthesized Pr-modified ceria nanocubes exhibit an enhanced oxidase-like activity on the organic dye TMB within a wide range of concentrations and durations. The oxidase activity increases with increasing Pr amounts in Pr-modified ceria nanocubes within the investigated concentration range. Meanwhile, these Pr-modified ceria nanocubes also show higher reducibility than pure ceria nanocubes. The kinetics of their oxidase mimetic activity is fitted with the Michaelis-Menten equation. A mechanism has been proposed on how the Pr incorporation could affect the energy level of the bands in ceria and hence facilitate the TMB oxidation reaction. The presence of Pr3+ species on the surface also contributes to the increasing activity of the Pr-modified ceria nanocubes present higher oxidase activity than pure ceria nanocubes.

Since only the molecules that are in direct contact with the TiO2 surface undergo photosensitization, it is challenging to regenerate the TiO2-impregnated chitosan (TIC) adsorbent beads under visible light. This study focused on the role of chitosan swelling properties. It was found that dye-loaded TIC adsorbent exhibited a pH-dependent swelling owing to protonation/deprotonation of free amino groups on chitosan chains. In the acidic medium (pH<6.0), the adsorbent underwent a 'smart' phase transition from a dry contracted state to a hydrated swollen state, and its physicochemical properties were also significantly changed, which eventually enabled the photosensitized oxidation of dye. This swelling induced regeneration was further confirmed by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The involvement of oxygen radical species (O2(-)/HOO and OH) was also confirmed with electron spin resonance (ESR) spectroscopy. Moreover, the adsorption effectiveness of TIC adsorbent was mostly recovered after six regeneration cycles.

In this paper, a thiol graphene-thiol chitosangold nanoparticles (thGP-thCTS-AuNPs) nanocomposites film with porous structure was fabricated by electrochemically depositing on glassy carbon electrode (GCE), which exhibited good biocompatibility and improved conductivity, to construct immunosensor free label for detection of carcinoembryonic antigen (CEA). The electrochemical behavior of this immunosensor was investigated by cyclic voltammetry. Under the optimum conditions, the immunosensor revealed a good amperometric response to CEA in two linear ranges (0.3-8.0 ng mL(-1) and 8.0-100 ng mL(-1)) with a detection limit of 0.03 ng mL(-1). The results indicated that the immunosensor has the advantages of good selectivity, high sensitivity, and good stability for the determination of CEA.

A new type of amphiphilic chitosan derivative, deoxycholic acid-hydroxypropyl chitosan (DCA-HPCHS), has been synthesized through coupling reaction between 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride, N-hydroxysuccinimide, and deoxycholic acid which acts as hydrophobic group. Physicochemical properties of DCA-HPCHS in aqueous media were studied by surface tension and fluorescence measurement. It was also used to prepare gold nanoparticles at room temperature by green synthesis. Results showed that DCA-HPCHS can be concentrated on the surface to decrease the surface tension, and to associate with hydrophobic chains to form aggregates in the solution. With increased degree of substitution of the hydrophobic group, the surface tension decreased at the same concentration of the derivative, and the aggregates formed at lower concentration of the derivative. The form and size of the aggregates were analyzed by transmission electron microscopy and dynamic light scattering, which showed that the aggregates were spherical, and the size of them in solution increased with increasing concentration. In biosynthesis of gold nanoparticles, DCA-HPCHS acts as reducing and stabilizing agent, and the pH of DCA-HPCHS solution influenced the shape and size of the gold nanoparticles. And the results indicate that it is a potential material used in green synthesis of metal nanomaterials.