We have demonstrated an ingenious one-pot aqueous domino-driven synthesis toward hollow hybrid spheres with ultrafine metal nitrides/oxides in hollow carbon cavity. The micelle-interfacial copolymerization is applied for shell formation, while the copolymerization-generated H⁺ spontaneously triggers oxometallate condensation for encapsulation. By regulating the synthetic conditions, the encapsulated metal species can be well tailored with different sizes/contents (nanocluster to several nanometers) and compositions (VN, VO, MoN, WN, bimetal-based nitrides). The ultrafine VN confined in hollow carbon exhibits excellent potassium storage performance.