Luminescent Zn₅-Based Covalent Metal–Organic Framework Showing ∼3.2 Å Pocket for Fluorescence Recognition and Determination of Ce(III)

We report herein the construction of a covalent metal–organic framework (CMOF-Zn5-1) based on a Zn5 building block. Notably, its stacking architecture affords interlayer pockets with a size of ∼3.2 Å, which is matchable with the size of rare earth ions, leading to fluorescence sensing of Ce3+ with a low detection limit of 90 nM (12.6 ppb) and a standard deviation of 8.5%, suggesting the superior application of CMOF-Zn5-1 for detecting Ce3+.