A highly dispersed cobalt(II) porphyrin (PhCo(II)) encapsulated inside a highly cross-linked poly(4-ethylstyrene-co-divinylbenzene) matrix (St-DVB) is investigated by means of FTIR, Raman, UV-Vis and EPR spectroscopies. The adoption of the highly porous St-DVB support is the key factor in reaching an optimum porphyrin dispersion in undiluted conditions ( approximately 10 wt% of porphyrin). It is demonstrated that the encapsulated PhCo(II) are characterized by the absence of any axial interactions involving the polymeric matrix, that can be considered a "non-coordinating" solvent. Finally, the permanent porosity of the encapsulating matrix allows gaseous molecules to reach the Co(II) cations also in the absence of swellable solvents. In particular, the reactivity of the isolated Co(II) porphyrin species towards nitric oxide (NO) is investigated, with possible implications in the understanding of the crucial role played by NO in biological systems.