A viologen-based host–guest Eu-MOF with visible photochromism and strong photoluminescence

A viologen-based host–guest metal–organic framework with both visible photochromism and strong photoluminescence was designed and synthesized, namely (H2bpyb)[Eu(btec)]2 (bpyb = 1,4-bis(4-pyridyl)benzene, H4btec = 1,2,4,5-pyromellitic acid), providing an effective pathway for designing multifunctional optical materials with comprehensive performance.