Cu/Fe-MOFs based on mixed ligands: synthesis, crystal structure and electrocatalytic hydrogen evolution performance

Two new metal-organic framework complexes Cu-MOF (C28H16Cu2N6O9S2) and Fe-MOF (C28H17FeN6O9S2) were synthesized with 4-[5-(pyridin-4-yl)-[1,3]thiazolo[5,4-d] [1,3]thiazol-2-yl]pyridine (Py2TTz) and pyridine-2,6-dicarboxylic acid (DPA) as mixed ligands. The single crystal X-ray diffraction results displayed that Cu2+ coordinated with Py2TTz and DPA to form 3D network structure while Fe2+ coordinated only with DPA to form 2D laminar structure, in which Py2TTz interspersed between bilayer iron complexes. The presence of Py2TTz enlarged the pore size of Fe-MOF, increasing its Brunauer-Emmett-Teller (BET) surface area and specific surface area, while the 3D structure of Cu-MOF facilitated electron transport and mass transfer. As a result, the hydrogen evolution reaction (HER) performance of Cu-MOF was slightly higher than that of Fe-MOF. This work provided an interesting idea for the design and synthesis of inexpensive HER electrocatalysts.