The structures and photochemical behaviour of two new metal–organic frameworks (MOFs) are reported. Reaction of Re(2,2′-bipy-5,5′-dicarboxylic acid)(CO) ₃ Cl or Mn(2,2′-bipy-5,5′-dicarboxylic acid)(CO) ₃ Br with LiCl or LiBr, respectively, produces single crystals of {Li ₂ (DMF) ₂ [(2,2′-bipy-5,5′-dicarboxylate)Re(CO) ₃ Cl]} _n ( ReLi ) or {Li ₂ (DMF) ₂ [(2,2′-bipy-5,5′-dicarboxylate)Mn(CO) ₃ Br]} _n ( MnLi ). The structures formed by the two MOFs comprise one-dimensional chains of carboxylate-bridged Li(I) cations that are cross-linked by units of Re(2,2′-bipy-5,5′-dicarboxylate)(CO) ₃ Cl ( ReLi ) or Mn(2,2′-bipy-5,5′- dicarboxylate)(CO) ₃ Br ( MnLi ). The photophysical and photochemical behaviour of both ReLi and MnLi are probed. The rhenium-containing MOF, ReLi , exhibits luminescence and the excited state behaviour, as established by time-resolved infrared measurements, is closer in behaviour to that of unsubstituted [Re(bipy)(CO) ₃ Cl] rather than a related MOF where the Li(I) cations are replaced by Mn(II) cations. These observations are further supported by density functional theory calculations. Upon excitation MnLi forms a dicarbonyl species which rapidly recombines with the dissociated CO, in a fashion consistent with the majority of the photoejected CO not escaping the MOF channels. This article is part of the themed issue ‘Coordination polymers and metal–organic frameworks: materials by design’.