Catalysts

This study investigates the synthesis, dual functional applications, and electrochemical performance of the amine-functionalized metal-organic framework (MOF), namely UiO-66-NH₂. The material was synthesized via the solvothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning and transmission electron microscopy (SEM/TEM). UiO-66-NH₂ was assessed as a catalyst for the reduction of nitroarenes, specifically 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP), under both dark and photo-assisted (i.e., photocatalysis) conditions. Complete photoreduction of nitroarenes was achieved under photocatalysis, highlighting its photo-assisted catalytic efficacy. UiO-66-NH₂ before and after nitroarenes adsorption capacities were investigated, and subsequent electrochemical assessments confirmed its suitability as a supercapacitor electrode. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analyses demonstrated that nitroarene adsorption and light irradiation markedly improved specific capacitance. 2-NP@UiO-66-NH₂ showed specific capacitance of 221 F/g at 1 A/g under UV radiation. UiO-66-NH₂ demonstrated remarkable cycling stability (100%) across 7000 cycles. Structural and property modifications of UiO-66-NH₂, adsorption of redox-active species, and photo-assisted mechanisms can significantly enhance the energy storage efficacy. The results illustrate the dual role of UiO-66-NH₂ as an effective photo-assisted catalyst and electroactive supercapacitor material, facilitating integrated environmental remediation and energy storage applications.

A promising route for removing antibiotics such as penicillin from wastewater is photocatalytic degradation under UV irradiation using TiO₂ nanoparticles. However, the microscopic mechanisms governing the initial degradation steps remain poorly understood. In particular, it is still unclear whether degradation preferentially occurs in solution or upon adsorption on the oxide surface, and which molecular sites are most vulnerable to attack in solution compared to those activated on the catalyst. In this work, we introduce a unified density functional theory approach that treats penicillin V (phenoxymethylpenicillin) consistently, both isolated in solution and adsorbed on an anatase TiO₂ nanocluster, enabling a direct comparison between solution-phase and surface-mediated degradation pathways. Within this framework, we analyze the adsorption configurations, energy-level alignment, charge-transfer pathways, UV-Vis absorption properties, local reactivity descriptors, and the initial steps leading to bond breaking. The results show that the direct photoexcitation of PenV followed by electron transfer to the oxide is less likely, due to the high energy of the pollutant’s excited states. In contrast, degradation initiated by the transfer of photogenerated holes from the catalyst to the adsorbed antibiotic appears more probable, driven by the smaller energetic offset and by the hybridization between molecular and oxide states. Overall, adsorption on the oxide surface appears to be more conducive to degradation, with the carbon atom in the β-lactam ring consistently identified as a susceptible site for attack across different environments.

The catalytic conversion of carbon dioxide to methanol is significantly important both practically and scientifically for the reduction in CO₂ emissions. Furthermore, it can partially address the issue of human reliance on non-renewable resources. The main motivation of this study is to use a melamine polymer network to support a copper-based catalyst for CO₂ hydrogenation to methanol. Based on Schiff base chemistry, a facile catalyst-free process, a novel porous polyaminal polymer (MGPN) was prepared with nitrogen contents as high as 38%. MGPN was used as a support for Cu-based catalyst and applied in CO₂ hydrogenation to CH₃OH under mild conditions. A deep characterization of the MGPN@CuO/ZnO/Al₂O₃ catalyst was made through FTIR, N₂ adsorption–desorption, SEM-EDS, TEM, TGA, XRD, CO₂-TPD, and H₂-TPR techniques. The CO₂ hydrogenation study was performed in a fixed bed reactor with a residence time of 1.104 s on varying parameters such as the metal loading, catalyst amount, flow rate, pressure, calcination temperatures, reduction temperatures, and catalytic reaction temperature profile. The space-time yield (STY) of 145.43 mg_methanol·g_catalyst⁻¹·h⁻¹, a selectivity of 98.36%, and CO₂ conversion of 11.76% were obtained under an economically and energetically sustainable low-pressure (1 MPa) and 260 °C hydrogenation process.