Author Identifier (ORCID)
Hussein Rasool Abid: https://orcid.org/0000-0003-3368-371X
Abstract
Global warming is primarily driven by the rapid accumulation of carbon dioxide (CO₂) in the atmosphere. Metal–organic frameworks (MOFs) have emerged as promising materials for mitigating CO₂ emissions due to their tunable porosity, large surface area, and structural flexibility. Among them, MIL-53(Al) has attracted widespread interest owing to its excellent thermal and chemical stability. Recent studies show that modifying MOFs with secondary metals can significantly enhance their CO₂ adsorption performance. In this work, a one-pot synthesis method was employed to incorporate calcium (Ca), functioning as a Lewis basic metal, into the MIL-53(Al) framework to produce a series of bimetallic materials: MIL-53(Al, Ca)-1, -2, and − 3. These materials were further treated with NaOH to yield MIL-53(Al, Ca, Na)-1, -2, and − 3. Introducing Ca into the framework increased the affinity toward CO₂—a Lewis acidic gas—thereby enhancing adsorption. All materials were characterised and compared with pristine MIL-53(Al). CO₂ adsorption was evaluated at 273 K under both low pressure (up to 100 kPa) and high pressure (up to 980 kPa), while N₂ adsorption was measured at 273 K and 100 kPa. N₂ uptake decreased significantly with increasing Ca content, from 0.7177 mmol·g⁻¹ for MIL-53(Al) to 0.173 mmol·g⁻¹ for MIL-53(Al, Ca)-3 and MIL-53(Al, Ca, Na)-3. Moderate Ca incorporation improved CO₂ adsorption: at 100 kPa, MIL-53(Al, Ca)-1 and MIL-53(Al, Ca, Na)-1 achieved 4.09 and 3.56 mmol·g⁻¹, respectively, compared with 2.19 mmol·g⁻¹ for MIL-53(Al). However, excessive Ca loading (samples − 3) reduced CO₂ uptake due to structural distortion and reduced surface area. Despite this, the highly Ca-modified samples (-3) exhibited superior CO₂/N₂ selectivity. These findings demonstrate that controlled Ca incorporation can tune the adsorption behaviour and separation efficiency of MIL-53-type MOFs, offering a promising pathway for designing high-performance adsorbents for CO₂ capture and CO₂/N₂ separation.
Keywords
Calcium, CO2 capture, CO₂ adsorption, gas separation, metal organic frameworks, MIL-53 (Al), N2 separation
Document Type
Journal Article
Date of Publication
4-1-2026
Volume
20
Issue
2
Publication Title
International Journal of Environmental Research
Publisher
Springer
School
Centre for Sustainable Energy and Resources
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Comments
Abid, H. R., Znad, H., Alawi, N. M., Rashid, F. L., Dulaimi, A., Alanazi, A., Keshavarz, A., Iglauer, S., & Wang, S. (2026). Enhancing CO2 adsorption and CO2/N2 separation performance by incorporating calcium in MIL-53 (AL). International Journal of Environmental Research, 20. https://doi.org/10.1007/s41742-026-01051-2