Polypeptides have attracted widespread attention as building blocks for complex materials due to their ability to form higher-ordered structures such as -sheets. However, the ability to precisely control the formation of well-defined -sheet-assembled materials remains challenging as -sheet formation tends to lead to ill-defined and unprocessable aggregates. This work reports a simple, rapid, and robust strategy to form well-defined peptide -sheet-assembled shells (i.e., hollow spheres) by employing surface-initiated N-carboxyanhydride ring-opening polymerization under a highly efficient surface-driven approach. The concept is demonstrated by the preparation of enzyme-degradable rigid shell architectures composed of H-bonded poly(L-valine) (PVal) grafts with porous and sponge-like surface morphology. The porous PVal-shells exhibit a remarkable and unprecedented ability to non-covalently entrap metal nanoparticles, proteins, drug molecules, and biorelevant polymers, which could potentially lead to a diverse range of biodegradable and functional platforms for applications ranging from therapeutic delivery to organic catalysis.