The authors introduce a novel class of cubic boronate ester cages (6) derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. These cages exhibit unprecedented stability under ambient conditions and in the presence of water or alcohols, due to steric shielding that prevents dynamic exchange at the Lewis acidic boron sites under neutral conditions. The cages are synthesized via a dynamic covalent approach and characterized by NMR, mass spectrometry, and X-ray crystallography. They demonstrate efficient encapsulation and release of β-carotene dyes and heterogeneous water oxidation catalysis using ruthenium catalysts, showcasing their potential for various applications in both solution and solid-state environments. The study highlights the importance of steric hindrance in stabilizing dynamic covalent materials and opens new avenues for the design of robust and versatile porous structures.The authors introduce a novel class of cubic boronate ester cages (6) derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. These cages exhibit unprecedented stability under ambient conditions and in the presence of water or alcohols, due to steric shielding that prevents dynamic exchange at the Lewis acidic boron sites under neutral conditions. The cages are synthesized via a dynamic covalent approach and characterized by NMR, mass spectrometry, and X-ray crystallography. They demonstrate efficient encapsulation and release of β-carotene dyes and heterogeneous water oxidation catalysis using ruthenium catalysts, showcasing their potential for various applications in both solution and solid-state environments. The study highlights the importance of steric hindrance in stabilizing dynamic covalent materials and opens new avenues for the design of robust and versatile porous structures.