An unexpected green phosphor! The promising activator‐free yttrium metal–organic framework (MOF) [Y5(OH)6(HCO2)3(CO3)2‐(C4O4)] ⋅2.5 H2O consists of unique {Y5O22} pentamers and four types of ligands, the carbonate group of which was unprecedentedly in situ generated from squaric acid. This pure yttrium–MOF compound displays intrinsic green light and has proven to be the first hybrid‐yttrium‐host lattice to achieve near‐white‐light solely through Eu3+ doping (see figure).