A new all-organic mesoporous cross-linked polymer (MCP-1) has been synthesized hydrothermally through in situ aqueous-phase radical polymerization of acrylic acid in the presence of a supramolecular assembly of cationic surfactant cetyltrimethylammonium bromide (CTAB) as the structure-directing agent (SDA) and N,N-methylene-bis-acrylamide as a cross-linker. After successful removal of the SDA molecules through solvent extraction, gold nanoparticles (GNPs) stabilized in the presence of positively charged tris(hydroxymethyl) aminomethane (TRIS) have been loaded into the mesopores through the electrostatic interaction with the –COO⁻ groups existing at the surface of the mesopores. Powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy/energy-dispersive spectrometry (FESEM-EDS), N₂ sorption, ¹³C cross-polarization magic angle spinning (¹³C CPMAS) NMR, Fourier transform infrared spectroscopy, and UV–visible spectroscopic analysis were carried out to characterize the solid mesoporous materials before and after GNP loading. XRD and HRTEM analyses demonstrated the existence of mesopores and a wormholelike disordered nanostructure. N₂ sorption data revealed good Brunauer–Emmett–Teller surface areas together with type IV isotherms for the MCP-1 samples. FESEM and UV–visible spectral measurements confirm the loading of GNPs. The electrode modified with GNP-loaded MCP-1 can efficiently catalyze the reduction of H₂O₂.