Hamidreza Mahdavi

Metal–organic frameworks (MOFs) have emerged as promising candidates for selective gas adsorption due to their tunable structures, high porosity, and numerous open metal sites (OMSs). This research synthesizes and characterizes bimetallic FexCo1–x-MOF-74 frameworks containing both iron (Fe) and cobalt (Co) metal centers to investigate and improve their oxygen (O2) adsorption performances. Monometallic Fe-MOF-74 and Co-MOF-74, as well as bimetallic versions with Fe/Co ratios of 0.1:0.9, 0.5:0.5, and 0.9:0.1, were synthesized by a solvothermal method. A thorough characterization analysis was performed to verify their structural integrity, porosity, thermal stability, and metal composition. O2 adsorption isotherms were assessed at 204, 273, and 298 K to analyze adsorption capacity and temperature-dependent characteristics. Cyclability experiments at 298 K examined the reusability of the materials during multiple adsorption–desorption cycles. Advanced characterization techniques, such as vibrating sample magnetometry (VSM), 57Fe–Mössbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS), unveiled the possible adsorption mechanism. The findings indicate that monometallic Fe-MOF-74 has a significant initial O2 adsorption capacity of 2.58 mmol/g at 298 K due to strong chemisorption at Fe sites. However, its cyclability is poor due to the irreversible oxidation of Fe2+ to Fe3+ at 298 K, resulting in a large drop after the first cycle. In contrast, Co-MOF-74 has a lower initial capacity of 0.36 mmol/g at 298 K, but demonstrates superior reversibility, maintaining consistent performance throughout several cycles owing to weaker, reversible physisorption. Among the bimetallic variants, Fe0.5Co0.5-MOF-74 achieves an optimum balance, exhibiting a moderate initial capacity of 0.82 mmol/g at 298 K and maintaining steady performance of around 0.65 mmol/g over seven cycles. The addition of Co stabilizes the Fe sites against oxidation and improves the material’s reusability. Mechanistic investigations demonstrate that Co mitigates Fe oxidation by facilitating reversible interactions and preventing the formation of irreversible Fe–O2 bonds. The results underscore the promise of bimetallic MOFs as adaptable platforms for effective and sustainable O2 capture, where the Fe/Co ratio can be adjusted to optimize adsorption capacity and cyclability.

Zeolitic imidazolate frameworks (ZIFs) have emerged as promising candidates for high O₂ adsorption capacity, O₂/N₂ selectivity and cyclability due to their tunable chemical and structural properties governed by the selection of organic ligands, metal centres and synthesis methods. Therefore, this research engineers ZIF-7, ZIF-8, ZIF-62 and their mixed-metal derivatives containing cobalt (Co) or iron (Fe) (ZIF-8-derived Fe-mIM where applicable) to improve O₂ adsorption. Because performance metrics trade off, no single ZIF maximised all objectives, and application-specific leads were identified. The highest O₂ capacity was delivered by ZIF-8(Zn : Co = 90 : 10)-MS, reaching 0.35 mmol g⁻¹ with selectivity of 2.01, and 9.9% decrease over 3 cycles. The greatest selectivity was achieved by ZIF-8-derived Fe-mIM material (Zn : Fe = 0 : 100)-MS, giving selectivity of 2.60 at a low adsorption of 0.09 mmol g⁻¹ and 9.6% loss over 3 cycles. The most robust 3-cycle performance was observed for ZIF-8-US, which retained capacity with 0.5% loss while providing 0.26 mmol g⁻¹ and selectivity of 1.06. For a balanced generalist over 3 cycles, ZIF-62-US offered the strongest overall combination, providing 0.34 mmol g⁻¹, selectivity of 1.01, and 1.3% loss. These results underscore the delicate balance among O₂ adsorption performance with structural integrity, coordination chemistry, adsorption characteristics, and cyclability in ZIFs shaped by organic ligand, metal centres, and synthesis method choices.

Plastics have revolutionised modern society; however, they have also caused environmental damage via waste accumulation. To balance their advantages with the negative impact on the environment, it is necessary to enhance recycling procedures, since the existing techniques are ineffective, require significant energy consumption, and yield recycled items of poor quality. One promising pathway is to utilise membranes. While membrane technology has been extensively studied in wastewater treatment and organic solvent recovery, its direct application to plastic recycling, particularly using real plastic feedstocks like PET, remains underexplored. This paper aims to address the gap by exploring different plastic recycling technologies, followed by an analysis of the current state of the art and then the prospective integration of membrane technology into plastic recycling processes with an emphasis on PET as a case study. This study provides a forward-looking discussion on some exciting opportunities including using conventional membrane processes and emerging membrane processes. These include separating impurities and additives from the recycling stream, recovery of valuable catalysts, and treating wastewater produced during PET recycling processes. This study also investigates emerging membrane research in PET recycling via use of mixed matrix membranes (MMMs) and implementation of hybrid membrane systems (HMSs). This study also aims to identify current challenges and future opportunities for membrane technology implementation in the field of plastic recycling, considering its impact on recycled product quality, energy consumption, and economic feasibility. Membrane technology is demonstrated to have the potential to transform the plastic recycling industry, and contribute to a more sustainable and circular economy.

The concept of non‐Crystalline Metal–Organic Frameworks (MOFs) is both theoretically exciting and rich in potential applications. Since their conceptual introduction, research in this field has experienced significant growth. This review provides a comprehensive overview of the design, synthesis, and applications of non‐crystalline MOFs, highlighting the current state of the art. It examines the fundamental principles of non‐crystalline MOFs, the various synthetic approaches, and the nature of non‐crystalline MOFs. Additionally, the review outlines their pathway from the laboratory to industrial applications, emphasizing challenges and opportunities for further development.

The purpose of this study was to design and develop a self-supporting glass MOF membrane (GMM) including its design, fabrication under different heat treatment temperatures, analysis of its physical–chemical properties, and assessment of its separation performance. Glass MOFs preserve metal–ligand bonding structures similar to their crystalline counterparts, providing intrinsic gas separation properties alongside the benefits of amorphous materials, including reduced grain boundaries and ease of processing. In this work, ZIF-62 was melted and then cooled to fabricate GMMs using vitrification to enhance molecular sieving. This study systematically examines the impact of varying thermal treatment temperatures (400–475 °C) on the physical and chemical transformations of GMMs, revealing their effects on the porosity, defect formation, and molecular sieving performance through advanced characterization techniques (e.g., solid-state nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), He pycnometry, and positron annihilation lifetime spectroscopy (PALS)). The optimal GMM exhibits an impressive separation performance, particularly for H2 separation. The GMM at 4 bar and 25 °C exhibited He, H2, CO2, N2, and CH4 gas permeations of 576.37, 509.23, 146.07, 3.45, and 2.28 barrer, respectively. The ideal selectivities of H2/CH4, CO2/N2, CO2/CH4, H2/N2, and H2/CO2 gas pairs were 223.47, 42.37, 64.10, 147.71, and 3.49, respectively, which significantly exceed earlier reported values for ZIF-62 membranes, demonstrating the significant potential for GMMs as high-performance molecular sieve membranes, particularly for H2 separation. This work by optimizing the vitrification process through systematic temperature control highlights GMM’s ability to achieve high selectivity and permeability, positioning it as a promising candidate for industrial gas separation applications.

Despite the known impacts on climate change of carbon dioxide emissions, the continued use of fossil fuels for energy generation leading to the emission of carbon dioxide (CO₂) into the atmosphere is evident. Therefore, innovation to address and reduce CO₂ emissions from industrial operations remains an urgent and crucial priority. A viable strategy in the area is postcombustion capture mainly through absorption by aqueous alkanolamines, which focuses on the separation of CO₂ from flue gas, despite its limitations. Within this context, porous materials, particularly metal-organic frameworks (MOFs), have arisen as favorable alternatives owing to their significant adsorption capacity, selectivity, and reduced regeneration energy demands. This research evaluates the engineering insights into tailored MOFs for enhanced CO₂ capture, focusing on three series of MOFs (ZIF, UiO-66, and BTC) to investigate the effects of organic ligands, functional groups, and metal ions. The evaluation encompassed a range of aspects including adsorption isotherms of pure gases [CO₂ and nitrogen (N₂)] and mixed gas mixture (CO₂ and N₂ with 15:85% ratio), along with utilization of the ideal adsorbed solution theory (IAST) to simulate multicomponent gas adsorption isotherms. Moreover, the reliability of IAST for mixed gas adsorption prediction has been investigated in detail. The research offers valuable insights into the correlation between the characteristics of MOFs and their effectiveness in gas separation and how these characteristics contribute to the differences between IAST predictions and experimental results. The findings enhance the understanding of how to enhance MOF characteristics in order to reduce CO₂ emissions and also highlight the need for advanced models that consider thermodynamic nonidealities to accurately predict the behavior of mixed gas adsorption in MOFs. As a result, the incorporation of MOFs with enhanced predictability and reliability into CO₂ capture industrial processes is facilitated.