Fabrication of Epoxy-based Monolithic Filters

The polymerization of epoxy-based monoliths was already published elsewhere [20 (link)], and the monolithic filter discs used in this work were produced with adjustments after published protocols [38 (link),39 (link)]. In short, polytetrafluoroethylene molds with 16.3 × 60.0 mm of internal diameter were used (Supplementary Figure S1a) to obtain monolithic filter columns that were cut into discs with height of either 3 or 10 mm (Supplementary Figure S1c,d). The porogenic reaction mixture consisting of toluene and tert-butyl methyl ether (60:40, v/v) was heated to 29 °C. Subsequently, the initiator boron trifluoride diethyl etherate (BF3·Et2O) in 1,4-dioxane (1:10, v/v) was added to a concentration of 1.25%, and the components were mixed thoroughly. Then, the monomer polyglycerol-3-glycidyl ether (monomer/porogenic mixture ratio 20:80, v/v) was added, and after vigorous mixing, the solution was filled into the molds and incubated for 45 min at 29 °C (Supplementary Figure S1b). Afterward, the resulting monolithic columns were removed from their molds, stored in methanol overnight and air-dried. Scanning electron microscopy of monolithic filters was performed on a ZEISS SIGMA VP Field Emission Scanning Electron Microscope (Carl Zeiss Microscopy GmbH, Jena, Germany) as described elsewhere in detail [31 (link)].