Cu-BTC (HKUST-1) metal–organic framework (MOF) is widely recognized for its carbon capture capability due to its unsaturated copper sites, high surface area, and well-defined porous structure. This study developed mixed matrix membranes (MMMs) using cellulose triacetate (CTA), incorporating bimetallic Ni-Cu-BTC MOFs for CO₂/CH₄ separation, and benchmarked them against membranes fabricated with monometallic Cu-BTC. CTA was selected for its biodegradability, membrane-forming properties, and cost-effectiveness. The optimized membrane with 10 wt.% Ni-Cu-BTC achieved a CO₂ permeability of 22.9 Barrer at 25 °C and 5 bar—more than twice that of pristine CTA—with a CO₂/CH₄ selectivity of 33.8. This improvement stems from a 51.66% increase in fractional free volume, a 49.30% rise in the solubility coefficient, and a 51.94% boost in the diffusivity coefficient. Dual-sorption model analysis further confirmed enhanced solubility and adsorption mechanisms. These findings establish CTA/Ni-Cu-BTC membranes as promising candidates for high-performance CO₂ separation in natural gas purification and related industrial processes.

Polydimethylsiloxane (PDMS) is commonly used in gas-separation studies because of its high CO₂ permeability and stable mechanical properties. In this work, mixed matrix membranes (MMMs) were prepared by incorporating the bimetallic MOFs Ni-Cu-MOF-74, Ni-Co-MOF-74, and Ni-Zn-MOF-74 into a PDMS matrix. The membranes were fabricated by solution casting and characterized by SEM, XRD, FT-IR, and BET analyses, which confirmed uniform filler dispersion and the successful incorporation of the MOF-74 structures. Single-gas permeation tests showed clear performance improvements with MOF loading. The best results were obtained for the membrane containing 1 wt.% Ni-Cu-MOF-74, which reached a CO₂ permeability of 3188.25 Barrer and a CO₂/N₂ selectivity of 35.10. The improvement is attributed to the accessible metal sites and high surface area provided by the MOF-74 framework, which enhanced adsorption–diffusion pathways for CO₂ transport. These results show that PDMS/MOF-74 mixed-matrix membranes are effective for CO₂/N₂ separation, with Ni-Cu-MOF-74 achieving the highest performance.

Ammonium ions, prevalent water contaminants, can become hazardous at high concentrations. To mitigate this risk, various adsorbents have been developed, yet the kinetics of their adsorption processes remain under investigation. In this study, we present the fabrication and comprehensive analysis of pure silica and silica/calcium chloride (CaCl ₂ ) composites. These materials were characterized using advanced techniques such as scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Additionally, pore and salt ratio analyses were conducted using BET and DFT methods. Ammonium ion adsorption efficiency was evaluated through ultraviolet–visible spectroscopy (UV/Vis). The results show that with an increase in the concentration of CaCl ₂ , more adsorption was observed. However, the kinetic analysis revealed that the experimental results followed the pseudo‐second‐order model and values of k ₂ show that mass transfer was slow with a 1% CaCl ₂ ‐based silica composite as compared to other samples. The intramolecular model predicted that the adsorption of ammonium ions was a two‐step process, and the Elovich model fits reasonably, highlighting the presence of physicochemical interactions between ammonium ions and CaCl ₂ ‐silica composites. Furthermore, these composites proved highly effective in treating aquarium water. The treatment process increased the pH from 6.19 to 6.74 and successfully removed up to 43% of ammonium ions from the aquarium water. These findings highlight the potential of silica/CaCl ₂ composites as a viable adsorbent for ammonium removal for aquarium water purification, offering a significant advancement in maintaining a safe environment for aquatic life. Practitioner Points: State‐of‐the‐art characterization techniques confirmed successful fabrication of Silica/Calcium Chloride (CaCl ₂ ) Hybrid Composites. The fabricated composites showed better ammonium ion adsorption, improving the effectiveness of water purification. Kinetic studies revealed a pseudo‐second‐order model, with a slower mass transfer rate in low CaCl ₂ concentration composites. The intramolecular model indicates a two‐step adsorption mechanism, while the Elovich model validates physicochemical interactions. Optimal composite improves the aquarium water pH from 6.19 to 7.08 by the removal ammonium ions.