Coordination Mode Engineering of Ce-Based Frameworks to Tune Photocatalytic Hydrogen Evolution

The coordination mode and multinuclear metal center can modulate the band gap ( E g) of metal–organic frameworks (MOFs), which is critical for photocatalytic reactions. Herein, three Ce-MOFs of Ce-1, Ce-2, and Ce-3 were synthesized with full, partial, and noncoordination of the bipyridyl moiety in the 2,2’-bipyridine-5,5′-dicarboxylate (bpdc 2– ) ligand, respectively. These MOFs were employed to explore their photocatalytic hydrogen evolution performance. With Pt nanoparticles as cocatalysts, the hydrogen evolution rate of Ce-3 reaches 12.99 μmol h –1, which is 3.61 times that of Ce-1 . Both experimental results and density functional theory (DFT) calculations demonstrate that the uncoordinated bipyridyl unit influences the photocatalytic efficiency. The more uncoordinated bipyridyl units correspond to smaller E g. Additionally, the oxygen and/or carboxylate bridged multinuclear Ce-centers in the MOFs facilitate an efficient ligand-to-metal charge transfer (LMCT). The insights from this study provide a strategic guideline for engineering coordination modes in MOFs to enhance their photocatalytic hydrogen production capacity.