Heterometallic cluster-organic frameworks with fascinating architectures and multi-functionality have the potential to be applied in various fields. However, in comparison with p–d, d–d, and d–f heterometallic cluster-organic frameworks, p–f heterometallic cluster-organic frameworks are far less explored even though they possess multiple merits. Herein, two novel isomorphic 4p–4f heterometallic cluster-organic frameworks based on high-nuclear [Ln₁₁Ge₁₂] (Ln = Pr, L1 and Nd, L2) second building units have been successfully synthesized via a hydrothermal approach by using bis(carboxyethylgermanium) sesquioxide (H₂E₂Ge₂O₃, E = –CH₂CH₂COO–). The [Ln₁₁Ge₁₂] cluster is constructed with two Ln-capped Ge₆-rings sandwiching a gear-like [Ln₉] unit. The as-prepared 4p–4f heterometallic [Ln₁₁Ge₁₂] cluster-organic frameworks possess two-dimensional (2D) layered structures. Moreover, the property study reveals the selective and sensitive luminescence sensing of Fe³⁺ with L1, exhibiting its promising application in environmental monitoring.