All primary data files of measurements and processed data of the journal article mentioned under related publications from Buchmeiser group can be found here. Further experimental for reproduction of experiments can be found in the Supporting Information. We report on the first ROMP-derived, poly(norborn-2-ene)-based monolithic supports with such tailored mesoporosity using a SiO2 nanowire (SNW) based hard templating approach that stongly differs form other hard templating approaches in that it provides access to defined mesopores. The resulting macroporous/mesoporous polymeric monoliths have a tailored mesoporosity in the 10–15 nm regime, transport pores in the micrometer range and allow for high linear flow rates (>2 mm s−1) at low back pressure (<6 bar). Together with the functional (OH) groups present, which can be used for catalyst immobilization, this morphological control over the meso- and macroporous structure offers access for use as catalytic microreactors. The hard templating process in combination with the solvent-induced phase separation (SIPS) process offers access to hybrid ROMP-derived monolithic structures. The surface-modified SNWs are incorporated into the structure-forming microglobule`s surface and can be removed with the aid of HF. By this approach, an increased mesoporosity with pore dimensions in the range of 5–30 nm, corresponding to the SiO2 nanowire diameter, is observed.