The [RuCl3(PCy3)2] complex presented high reactivity toward ring opening metathesis polymerization (ROMP) of norbornadiene (NBD) in a non-degassed solution upon addition of ethyl diazoacetate (EDA). Quantitative yields of polyNBD were obtained instantaneously at 25 °C. ROMP of norbornene (NBE) occurred better at 50 °C for 60 min, with 95% of isolated polyNBE. Copolymers with different porous structures were obtained from ROMP of NBE in the presence of NBD with different starting [NBE]/[NBD] molar ratios at 25 °C. SEM micrographs showed a more organized porous structure as the NBD loading decreased. A well-defined honeycomb-like pattern was recorded for the copolymer from the run with an NBE:NBD molar ratio load of 5000:500. The Tg values varied from 37 °C in polyNBE to 90 °C in poly[NBE-co-NBD] as the NBD loading increased.