Photocatalytic　synthesis　of　H2O2　is　an　advantageous　and　ecologically　sustainable　alternative　to　the　conventional　anthraquinone　process.　However,　achieving　high　conversion　efficiency　without　sacrificial　agents　remains　a　challenge.　In　this　study,　two　covalent　organic　frameworks　(COF-O　and　COF-C)　were　prepared　with　identical　skeletal　structures　but　with　their　pore　walls　anchored　to　different　alkyl　chains.　They　were　used　to　investigate　the　effect　of　the　chemical　microenvironment　of　pores　on　photocatalytic　H2O2　production.　Experimental　results　reveal　a　change　of　hydrophilicity　in　COF-O,　leading　to　suppressed　charge　recombination,　diminished　charge　transfer　resistance,　and　accelerated　interfacial　electron　transfer.　An　apparent　quantum　yield　as　high　as　10.3　%　(lambda=420　nm)　can　be　achieved　with　H2O　and　O-2　through　oxygen　reduction　reaction.　This　is　among　the　highest　ever　reported　for　polymer　photocatalysts.　This　study　may　provide　a　novel　avenue　for　optimizing　photocatalytic　activity　and　selectivity　in　H2O2　generation.