The effective, stable, and secure catalysts are essential for sulfate radical (SO₄^·−)-based advanced oxidation processes (SR-AOPs) to the degradation of organic contaminants in water. Heterogeneous supported cobalt-based catalysts are commonly used to activate peroxymonosulfate (PMS) to achieve the degradation. In this work, we synthesized Co₃O₄@Al₂O₃ three-dimensional (3D) mesoporous nanocomposite (denoted as Co₃O₄@Al₂O₃ 3DPNC) in just one step by calcining cheap and green deep eutectic solvent (DES) solution containing Co salt. Co₃O₄@Al₂O₃ 3DPNC with the high specific surface area (93.246 m²/g), uniform pore distribution (3.829 nm) and rich porosity (0.255 cm³/g) were attained in a beautiful hierarchical structure which exhibited the open 3D propeller-like microstructure, two-dimensional lamellar substructure with rich folds, as well as the decoration of highly dispersed Co₃O₄ nanoparticles on mesoporous amorphous Al₂O₃. The excellent chemical and thermal stability of Al₂O₃ ensures the high stability of the catalyst, and the formation of the complex hierarchical structure makes the active Co₃O₄ be homogenously dispersed for effective catalysis. The catalyst demonstrated outstanding performance for catalytic degradations of organic pollutants (acetaminophen, oxytetracycline, 5-sulfosalicylic acid, orange G and Rhodamine B) by generated SO₄^·−, ·OH and ¹O₂. With a very low cobalt content (equal to 28.2 mg/L of Co), the catalyst exhibited very high stability and excellent reusability in the recycling usages, while the leaching of the cobalt element (< 0.145 mg/L) was also at a low level. Our catalyst achieved effective degradations of acetaminophen in cycles without losing its stable hierarchical nanostructure.

The development of highly active catalysts is the key to the successful application of sulfate radical (SO₄^·−)-based advanced oxidation processes (AOPs) to wastewater treatment. Herein, bimetallic oxide CoMn₂O₄ hierarchical porous nanosheets (CoMn₂O₄ HPNSs) were constructed using glucose/urea deep eutectic solvent (DES) as sustainable solvent and self-formed sacrificial carbon templates. The prepared CoMn₂O₄ HPNS exhibited outstanding peroxymonosulfate (PMS) activation performance, achieving the rapid degradation of refractory organic compounds in wastewater, including 5-sulfosalicylic acid (100%), acetaminophen (100%), oxtetracycline (100%), and sulfamethoxazole (91%) within 20 min. This excellent performance was attributed not only to the synergistic catalytic effect of Co-Mn bimetals, but also to the hierarchical porous structure which exposes more active sites and accelerates the migration of PMS and organic pollutants. In addition, CoMn₂O₄ HPNS also showed excellent reusability and high stability in multiple cycles of degradation. The active species quenching results and electron paramagnetic resonance measurements revealed that SO₄^·− greatly contributed to organic degradation, while ¹O₂ and ·OH also involved. Moreover, a series of other transition metal oxides (Co₃O₄, Fe₂O₃, Mn₃O₄, NiO, and CoFe₂O₄) with hierarchical porous nanosheet structures were successfully fabricated with this method. This study provides a simple, general, and low-cost strategy for fabricating hierarchical porous transition metal oxides, which are promising for the environmental remediation or many other applications in the future.

Polymer stabilizers are widely used to synthesize gold nanoparticles (Au NPs) to prevent their aggregation and improve their stability. Although stabilizers are known to greatly influence both the structure and size of Au NPs, limited efforts explore their effects on the activity of Au NPs for biocatalysis. Herein, different polymers are used as stabilizers to synthesize Au NPs. For the glucose oxidase-like activity, we find that without the spatial barrier from stabilizers, naked Au NPs show significantly high catalytic activity as well as the worst stability. Among the polymers, polyacrylic acid-stabilized Au NPs exhibit the highest activity, whose V_max (0.74 μM·s⁻¹) is higher than that of the natural glucose oxidase (0.37 μM·s⁻¹) due to the smallest particle size (< 2 nm) and the weak spatial resistance of polyacrylic acid. These variable catalytic results derive from the comprehensive effects including size, steric hindrance, and electronic effect. However, further selectivity and activity tests have exposed shortcomings. They possess universal activities for aldose oxidation, whereas cannot retain activities in typical physiological environments. Our findings highlight the role of polymer stabilizers in imposing effects on the glucose oxidase-like activity of Au NPs and provide a basis for further Au NPs engineering and applications.

Transition metal phosphides (TMPs) are essential catalysts for some general catalytic reactions. However, their potentials for biological catalysis have seldom been explored. Herein, we investigated the enzyme-like properties of four TMPs (FeP, CoP, Ni₂P, and Cu₃P) towards two sugar-related reactions. Among the four TMPs, Cu₃P nanoparticles (NPs) efficiently catalyzed the hydrolysis of glycosidic bonds as glycoside hydrolase mimics, and FeP NPs possessed both glucose oxidase-like (GOx-like) and peroxidase-like activities, which combined into a cascade reaction for glucose’s simple and one-step colorimetric biosensor without GOx. Cu₃P and FeP NPs with distinctive enzyme-like activities have shown unique biological catalysis potentials for further applications with an attractive and challenging goal of developing nanomaterials to mimic natural enzymes, which encourages more efforts to reveal TMP’s capabilities towards biocatalysis.

High-entropy-oxides (HEOs), a new class of solids that contain five or more elemental species, have attracted increasing interests owing to their unique structures and fascinating physicochemical properties. However, it is a huge challenge to construct various nanostructured, especially low-dimensional nanostructured HEOs under the high temperature synthetic conditions. Herein, a facile strategy using glucose-urea deep eutectic solvent (DES) as both a solvent and the carbon source of structure-directed template is proposed for the synthesis of various HEOs with two-dimentional (2D) nanonets and one-dimentional (1D) nanowires, including rock-salt (Co, Cu, Mg, Ni, Zn)O, spinel (Co, Cr, Fe, Mn, Ni)₃O₄, and perovskite La(Co, Cr, Fe, Mn, Ni)O₃. The as-prepared HEOs possessed five or more uniformly dispersed metal elements, large specific surface areas (more than 25 m²·g⁻¹), and a pure single-phase structure. In addition, high cooling rate (cooling in air or liq-N₂-quenching) was indispensable to obtain a single-phase rock-salt (Co, Cu, Mg, Ni, Zn)O because of phase separation caused by copper. By taking advantage of unique features of HEOs, rock-salt (Co, Cu, Mg, Ni, Zn)O can function as a promising candidate for lithium-ion batteries (LIBs) anode material, which achieved excellent cycling stability. This work provides a feasible synthetic strategy for low-dimensional hierarchical HEOs, which creates new opportunities for the stable HEOs being highly active functional materials.