• A novel combination of 3D printing, phase inversion, and MPECVD enables metal-free growth of B,N-doped carbon nanostructures on polymer-derived substrates, increasing electrochemically active surface area by 20-fold.
• The optimized electrodes exhibit up to 180% higher surface area-to-volume ratio and significantly improved mass transport, as guided by computational fluid dynamics simulations.
• Electrochemical oxidation of β-blockers (atenolol, metoprolol, propranolol) shows 4.7-, 4-, and 6.5-fold faster degradation rates, respectively, compared to non-optimized analogues.
• This catalyst-free, scalable approach offers a sustainable solution for removing emerging contaminants from wastewater, simplifying fabrication and reducing material contamination.