A Cu(PO3-C13H9)·H2O hybrid compound has been synthesized by a hydrothermal method from Cu(NO3)2·3H2O and 9H-fluorene-2-phosphonic acid [C13H9PO(OH)2]. Its structure was determined by X-ray diffraction performed on a single crystal. The compound crystallizes in the monoclinic centrosymmetric space group P21/a [a = 7.4977(5), b = 7.5476(5), c =22.3702(16) Å, β = 97.794(3)°, V = 1254.23(15) Å3, Z = 4]. Its lamellar structure consists of alternating organic and inorganic layers. Its organic sub-network is made up of a double layer of fluorene molecules, and its inorganic layer is composed of copper(II) dimers connected to phosphonate groups. In the structure, the neighbouring fluorenyl planes are almost orthogonal to each other, which indicates the absence of π stacking. A study of its magnetic properties, performed on a polycrystalline powder sample, showed antiferromagnetic interactions between the spin carriers without any ordering down to 1.8 K. The interactions between the two copper(II) species within the dimers were evaluated at J = –6.13(5) cm–1 with respect to the spin Hamiltonian H = –JSCu1SCu2. A fluorescence study under excitation at 266 nm showed the disappearance of fluorescence emission in the solid state. This has been attributed to fluorescence quenching by the metallic counterpart.