Harnessing Temperature‐Dependent Breathing Behaviour in Aluminium‐Based MOF for Enhanced Congo Red Dye Removal

ABSTRACT A novel and efficient strategy for dye adsorption is provided by unlocking the temperature‐dependent breathing behaviour of aluminium‐based metal–organic frameworks (Al‐MOF). Distinct from conventional MOF adsorption studies, this research uniquely elucidates the dynamic structural adaptations of Al‐MOFs that enable the accommodation of large dye molecules, specifically Congo red (CR). Hydrothermally synthesised Al‐MOFs—extensively characterised to confirm exceptional crystallinity, high porosity (BET surface area of 173 m 2 g −1 ), and thermal stability—exhibit a remarkable temperature‐responsive ‘breathing’ mechanism. Elevated temperatures induce reversible phase transitions from narrow to large pores, resulting in a significant expansion of pore volume that dramatically enhances CR adsorption, achieving a maximum capacity of 223.8 mg g −1 . The adsorption behaviour conforms to the Langmuir model (R 2 > 0.990) and follows pseudo–second‐order kinetics (R 2 = 0.993), confirming homogeneous chemisorption. Thermodynamic analysis indicates that the adsorption process is both spontaneous (ΔG° < 0 at ≥ 303 K) and endothermic (ΔH° = +82.06 kJ mol −1 , ΔS° = +271.7 J mol −1 K −1 ), further substantiating the role of the breathing mechanism. Importantly, the Al‐MOF demonstrates outstanding reusability, retaining over 90% adsorption efficiency after five cycles. These findings firmly establish temperature‐responsive breathing Al‐MOFs as transformative, thermodynamically favourable, and highly reusable adsorbents, offering a promising solution for the advanced environmental remediation of hazardous dye pollutants.