<p>A series of thermosetting polymers of 1,2,4,5-tetrahydroxtbenzene (THB) were synthesized as a model of a cross-linked polymer (PTHB) for photocatalytic H₂O₂ production. The THB unit was partially oxidized to a quinone species in the PTHBs during polymerization to form a quinhydrone complex with a THB unit in an adjacent polymer chain. The molecular structures of the PTHBs were modified by controlling the molar ratio of the cross-linker (chloromethyl methyl ether, CMME) to THB. The structure of the polymer was partially identified using solid-state DD-MAS ¹³C-NMR and IR spectroscopy. PTHBs were dispersed in distilled water and irradiated with visible light (100&#xa0;mW&#xa0;cm⁻², 1&#xa0;h) under O₂ bubbling to generate H₂O₂. The action spectrum of PTHB-C2 showed a good correlation with the diffuse reflection spectrum, indicating that PTHB-C2 is the active species for photocatalytic H₂O₂ generation. The activity of H₂O₂ generation was maximum at a CMME/THB ratio of two in the series of PTHBs. The trend in photocatalytic activity depending on the CMME/THB molar ratio correlated with the ketone fraction in PTHB.</p> Graphical abstract <p> Reaction scheme for H₂O₂ production on cross-linked polymers of 1, 2, 4, 5-tetrahydroxybenzenes.</p>