In coordination-driven metal-organic cages, the transition metal ions are generally utilized as linkages. Employment of its unique properties with the aim of achieving specific applications still presents great challenges. Herein, we report a decametric metal-organic cage named pentagonal prism (Mn20LC10) based on Tpy-Mn(II)-Tpy connectivity (Tpy = 2,2':6',2″-terpyridine) in which Mn(II) serves as a linker and endows the resulting metal-organic cage with good photosensitivity. In the photooxidation of benzaldehyde, pentagonal prism Mn20LC10 showed a significantly increased level of 1O2 production, the fastest conversion time, good recyclability, and substrate versatility due to its greatly improved intersystem crossing ability. Notably, the abundant active sites of metal pentagonal prism Mn20LC10 enable its photooxidation under solvent-free and daylight conditions. This work provides approaches for the development of inexpensive, green, and low-cost photosensitizer systems.