Coal-fired power generation remains a major source of carbon dioxide (CO₂) emissions, and metal–organic framework-74 (MOF-74) materials offer high adsorption capacity but rely on costly 2,5-dihydroxyterephthalic acid linkers that limit scalability. This study synthesized bimetallic Zn_0.75Mg_0.25-MOF-74 using terephthalic acid (TPA) as a cheaper alternative linker and evaluated the effect of synthesis reaction temperature (89–160 °C) and time (5–55.5 h) on its physicochemical properties for carbon capture. Samples were prepared solvothermally and characterized by FTIR, XRD, SEM-EDS, and N₂ (77 K) and CO₂ (293 K) adsorption analysis. FTIR confirmed metal–ligand coordination; XRD verified crystalline MOF-74 formation, and SEM showed well-defined rod-like morphology at 100 °C, 12 h and 125 °C, 30 h. Direct CO₂ adsorption on the 125 °C, 30 h sample yielded a Type I isotherm characteristic of micropore filling, with an uptake of 0.31 mmol/g at ~1 bar and 0.072 mmol/g at flue-gas-relevant conditions (~0.135 bar). Its CO₂-derived BET surface area (60.10 m²/g) and Dubinin–Astakhov micropore area (131.69 m²/g) far exceeded N₂-derived values, confirming ultra-micropores accessible to CO₂ but not to N₂ at 77 K. TPA therefore yields a stable, microporous CO₂-adsorbing framework, trading some capacity for lower cost and scalability. Future investigations should systematically evaluate long-term cycling stability and adsorption performance under mixed-gas operating conditions.

The development of bimetallic metal–organic frameworks (BMOFs) represents a promising strategy to meet critical requirements of CO₂ capture in flue gas, where CO₂ exists at low partial pressure (0.15 bar, 298–333 K) due to the synergistic effects of mixed-metal incorporation that can enhance stability and CO₂ affinity. In this study, aluminum and manganese were coordinated on terephthalic acid to produce a series of bimetallic Al-MIL-53-(Mn) with varying Mn/Al molar ratios. These samples were synthesized via a hydrothermal approach, followed by a two-step activation, and characterized using FTIR, PXRD, SEM-EDX, TGA, and the BET method to uncover fundamental CO₂ adsorption characteristics. All samples exhibited MIL-53 features, including a predominant microporous structure, the presence of hydroxyl bridging groups in the surface chemistry, a rhomboidal morphology that supports their breathing behavior, and high thermal stability. The textural properties and the crystallinity were enhanced with increased mixed-metal ratios (Mn/Al = 0.15, 0.45, 0.65), and the findings revealed structural destabilization at a high molar ratio (Mn/Al = 0.85). Besides the 77 K low-pressure N₂ isotherms, CO₂ isotherms measured at a screening temperature of 273 K demonstrated a maximum uptake of 3.03 mmol/g, which compares favorably with the 2.19–2.85 mmol/g reported in the literature for pristine MIL-53(Al). They revealed a consistent Type I Langmuir isotherm with a steep uptake at low partial pressure, which suggests the presence of strong preferential binding sites for CO₂ on the surface of bimetallic MOFs. As this is a screening study, the bulk Mn content (ICP-OES), the CO₂/N₂ selectivity derived from 273 K and 298 K isotherms, the performance at flue-gas temperatures (313–333 K) and moisture tolerance remain to be established.