Using volumetric adsorption techniques, we have measured the adsorption of argon on Cu-3(BTC)(2)(H2O)(3), (BTC = benzene-1,3,5-tricarboxylate), a microporous metal-organic framework structure, at temperatures between 66 and 143 K. In addition to the experiments, we have used Grand Canonical Monte Carlo simulations to calculate the adsorption isotherm of argon at 87 K. Our experimental and theoretical results are compared to those of previous studies. The experiments were performed using a high density of points, allowing us to obtain, in detail, the isosteric heat's coverage dependence. Our values from the simulations are in reasonable agreement with those obtained in the experiments.