Two-dimensional metal-organic nanosheets (MONs) combine the topological and chemical versatility of metal-organic frameworks (MOFs) with the advantages of 2D materials, yet their top-down synthesis remains limited mainly to systems with labile coordination bonds. Here, we report a top-down strategy to access MONs from robust 3D MOFs via in-plane covalent bond excision using clip-off chemistry. This approach enables formation of crystalline, porous 2D layers from otherwise nonexfoliable 3D Zr-polycarboxylate frameworks, expanding the scope of accessible MON architectures. Compared to the parent MOF, the resulting MONs exhibit enhanced catalytic performance in esterification reactions, due to the improved exposure of outer active sites.