Akademik Veri Yönetim Sistemi
INORGANIC CHEMISTRY, cilt.61, sa.9, ss.3931-3941, 2022 (SCI-Expanded)
The elucidation of the ideal coordination environment of a catalytic site has been at the heart of catalytic applications. Herein, we show that the water oxidation activities of catalytic cobalt sites in a Prussian blue (PB) structure could be tuned systematically by decorating its coordination sphere with a combination of cyanide and bidentate pyridyl groups. K-0.1[Co(bpy)](2.9)[Fe(CN)(6)](2) ([Cobpy-Fe]), K-0.2[Co(phen)](2.8)[Fe(CN)(6)](2) ([Cophen-Fe]), {[Co(bpy)(2)](3) [Fe(CN)(6)](2) 1[Fe(CN)(6)](1/3) ([Cobpy2-Fe]), and {[Co(phen)(2)](3)[Fe(CN)(6)](2)}[Fe(CN)(6)](1/3) CI0.11 ([Cophen2 - Fe]) were prepared by introducing bidentate pyridyl groups (phen: 1,10-phenanthroline, bpy: 2,2'-bipyridine) to the common synthetic protocol of Co-Fe Prussian blue analogues. Characterization studies indicate that [Cobpy2-Fe] and [Cophen2-Fe] adopt a pentanu- clear molecular structure, while [Cobpy-Fe] and [Cophen-Fe] could be described as cyanide-based coordination polymers with lower-dimensionality and less crystalline nature compared to the regular Co-Fe Prussian blue analogue (PBA), K0.1Co2.9[Fe(CN)(6)](2)([Co-Fe]). Photocatalytic studies reveal that the activities of [Cobpy-Fe] and [Cophen-Fe] are significantly enhanced compared to those of [Co-Fe], while molecular [Cobpy2-Fe] and [Cophen2-Fe] are inactive toward water oxidation. [Cobpy-Fe] and [Cophen-Fe] exhibit upper-bound turnover frequencies (TOFs) of 1.3 and 0.7 s(-1), respectively, which are similar to 50 times higher than that of [Co-Fe] (1.8 X 10(-2) s(-1)). The complete inactivity of [Cobpy2-Fe] and [Cophen2-Fe] confirms the critical role of aqua coordination to the catalytic cobalt sites for oxygen evolution reaction (OER). Computational studies show that bidentate pyridyl groups enhance the susceptibility of the rate-determining Co(IV)-oxo species to the nucleophilic water attack during the critical O-O bond formation. This study opens a new route toward increasing the intrinsic water oxidation activity of the catalytic sites in PB coordination polymers.