Copper is a common element in the environment and human body. Exposure to high concentrations of Cu2+ potentially causes health issues, such as Wilson and Alzheimer's diseases. It is of great importance for the highly selective and sensitive detection of Cu2+. In this work, a porous metal-organic framework (MOF), PCN222, is employed for the selective and sensitive determination of Cu2+. The selectivity of PCN222 relies on the interaction between Cu2+ and the porphyrin core of PCN222. PCN222 stacked with porphyrin rings exhibits solvent adaptability, which overcomes the drawback of the natural porphyrinic enzyme (such as HRP). PCN222 is used for constructing a sensor which shows a linear range of Cu2+ concentration from 0.4 to 13 μmol L-1, and its limit of detection (LOD) is 50 nmol L-1. The response time is less than 3 s, which is faster than previous methods. This work opens up a new route to MOF applications in the detection of metal ions in complex environments.