<p>Hyperpolarized ¹²⁹Xe magnetic resonance imaging (MRI) is a powerful tool for detecting respiratory system diseases. However, ¹²⁹Xe is an inert gas and lacks specific detection capability. Entrapping xenon within molecular cages to enable specific detection is a challenging task, and numerous molecular cages have been developed and evaluated to address this challenge. Herein, we report that the aluminum-based metal-organic framework, CAU-1, can effectively entrap xenon for hyperpolarized ¹²⁹Xe MRI in aqueous solutions. This platform exhibits high water stability and good dispersibility, and shows excellent xenon entrapment capability, even at a concentration as low as 50 µg/mL. Importantly, it is responsive to pH changes across a range from 6.6 to 5.0, making it promising for monitoring the weakly acidic environment in tumors or metabolic abnormality. Furthermore, the scalable and cost-effective production of this molecular cage will facilitate future advancements in molecular imaging and chemical sensing applications.</p>