Metal–organic framework-enabled CO₂ storage: Microstructural and mechanical performance investigation in cement-based materials

Rising anthropogenic CO₂ emissions drive global climate change, highlighting the need for scalable carbon-capture and storage solutions. While the CO₂ adsorption mechanisms of Metal–Organic Frameworks (MOFs) are well established, their direct utilisation for air capture and long-term CO₂ storage within cementitious materials remains unexplored. This study presents the first systematic investigation of direct CO₂ capture and storage in cementitious materials using MOFs, with potential for large-scale sequestration. Three MOFs (ZIF-8, UiO-66, and UiO-66-NH₂) were synthesised and compared to evaluate their effects on the microstructure and mechanical behaviour of cement-based materials. The mechanochemical synthesis minimised solvent use while yielding highly crystalline structures with under-coordinated metal centres, enhancing CO₂ capture. UiO-66-NH₂ exhibited the highest CO₂ uptake and selectivity at 298 K, approximately 2.5 mmol·g⁻¹ and 38, respectively, with good alkaline stability. When pre-loaded with CO₂ and incorporated at 0.1 wt%, UiO-66-NH₂ increased 28-day paste strength by 13.39% through amine-enhanced CO₂ affinity and strong interfacial bonding, whereas ZIF-8 promoted early portlandite consumption and formed finely dispersed carbonate–AFm deposits. Thermogravimetric and phase analyses confirmed that CO₂-loaded MOFs act as distributed micro-reactors, mineralising CO₂ in situ and densifying the microstructure. This study establishes, for the first time, MOFs for CO₂ capture and storage in cement-based materials.