Visible-Light-Driven Photocatalysts of Metal–Organic Frameworks Derived from Multi-Carboxylic Acid and Imidazole-Based Spacer

Five new metal–organic frameworks [M­(btec)0.5(bimb)]n (1) (M
= Co (1), Ni (2), Cu (3), Zn
(4)) and [Cd­(btec)0.5(bimb)0.5]n (5), were obtained by reactions
of the conjugated
1,2,4,5-benzenetetracarboxylic acid (H4btec) and 4,4′-bis­(1-imidazolyl)­biphenyl
(bimb) with corresponding metal salts under hydrothermal conditions,
respectively. MOFs 1-5 show different structures
and topologies: compounds 1 and 4 are isomorphic,
which possess typical PtS 3D nets; compound 2, 3 and 5 exhibit 2D layer structure, NbO 3D network and (4,6)-connected 3D binodal topology, respectively.
Notably, compounds 1, 2, and 5 represent the rare example of MOFs-based visible-light-driven photocatalysts
and show good stability toward photocatalysis. Furthermore, compound 5 is photocatalytically more active than 1 and 2 because of the relatively narrower band gap calculated from
LMCT transitions. In addition, the formation rate of •OH radicals
on compound 5/H2O interface via photocatalytic
reactions is much higher than that of 1 and 2, implying that the formation rate of •OH radicals during
photocatalysis is in agreement with photocatalytic activity and the
formation rate of •OH radicals is an important factor influencing
photocatalytic performance.