| Summary: | New microporous homopolymers were readily prepared from norbornadiene-2,5, its dimer and trimer by addition (vinyl) polymerization of the corresponding monomers with 60⁻98% yields. As a catalyst Pd-<i>N</i>-heterocyclic carbene complex or Ni(II) 2-ethylhexanoate activated with Na<sup>+</sup>[B(3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)<sub>4</sub>]<sup>−</sup> or methylaluminoxane was used. The synthesized polynorbornenes are cross-linked and insoluble. They are glassy and amorphous polymers. Depending on the nature of the catalyst applied, BET surface areas were in the range of 420⁻970 m<sup>2</sup>/g. The polymers with the highest surface area were obtained in the presence of Pd-catalysts from the trimer of norbornadiene-2,5. The total pore volume of the polymers varies from 0.39 to 0.79 cm<sup>3</sup>/g, while the true volume of micropores was 0.14⁻0.16 cm<sup>3</sup>/g according to t-plot. These polymers gave CO<sub>2</sub> uptake from 1.2 to 1.9 mmol/g at 273 K and 1 atm. The porous structure of new polymers was also studied by means of wide-angle X-ray diffraction and positron annihilation lifetime spectroscopy.
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