We consider a slit-like pore filled with a disordered hard-sphere matrix. The diameter of matrix species is chosen almost equal to the pore width. Another hard-sphere fluid species, of smaller diameter, enters, at a given chemical potential, into this confined quenched microporous medium. The model is similar to the experimental setup; see G. Cruz de Leon et al. Phys. Rev. Lett. 81, 1122 (1998). The model is solved by using the inhomogeneous replica Ornstein-Zernike equations with Percus-Yevick approximation. We discuss the effective interactions between species in a confined medium on the chemical potential and matrix microporosity.