Core–shell and multivariant metal–organic frameworks (MOFs) of the PCN-224 type were prepared using metal-free and metalated porphyrin building blocks. Probing these MOFs with luminescence quenching upon exposure to oxygen reveals efficient gas transport and oxygen quenching in the core of the MOF. Undesirable energy transfer results in diminished contribution of the phosphorescent component in all mixed MOFs except for the physical mixture of individual crystals used as a reference.