Atomically dispersed Cu-N3 on hollow spherical carbon nitride for acetaminophen degradation: Generation of 1O2 from H2O2

•Single atom Cu in the configuration of Cu-N3 was anchored on hollow spherical g-C3N4 to form SACu-hsCN.•The acetaminophen degradation activity of SACu-hsCN was superior to the sample of AGCu-hsCN with aggregated Cu particles via H2O2 activation.•The SACu-hsCN/H2O2 system degraded acetaminophen with a good durability.•1O2 unusually played a dominant role in degradation rather than the common OH radicals.