Structure-Activity Relationships in Ni- Carboxylate-Type Metal-Organic Frameworks' Metamorphosis for the Oxygen Evolution Reaction

Metal-organic frameworks (MOFs) have been reportedto catalyzethe oxygen evolution reaction (OER). Despite the established linksbetween the pristine MOFs and their derived metal hydroxide electrocatalysts,several limitations still preclude understanding of the critical factorsdetermining the OER performance. Of prime importance appears the choiceof MOF and how its compositions relate to the catalyst stability andin turn to the reconstruction or metamorphosis mechanisms into theactive species under OER conditions. An isoreticular series of Ni-carboxylate-typeMOFs [Ni-2(OH)(2)L] was chosen to elucidate theeffects of the carboxylate linker length expansion and modulationof the linker-linker pi-pi interactions (L= 1,4-benzodicarboxylate, 2,6-napthalenedicarboxylate, biphenyl-4,4 '-dicarboxylate,and p-terphenyl-4,4 ''-dicarboxylate). Degradationand reconstruction of MOFs were systematically investigated. The linkercontrols the transformation of Ni-MOF into distinct nickel hydroxidephases, and the conversion from alpha-Ni-(OH)(2) to beta-Ni-(OH)(2), thus correlating the Ni-MOF composition with the OER activityof the Ni-MOF-derived metastable nickel hydroxide phase mixture.

Automated summary

Metal-organic frameworks (MOFs) have been used for catalyzing the oxygen evolution reaction (OER), but the critical factors determining OER performance are still not well understood. In this study, an isoreticular series of Ni-carboxylate-type MOFs was chosen to investigate the effects of carboxylate linker length and linker-linker pi-pi interactions on MOF degradation and reconstruction. The results showed that the linker controlled the transformation of MOF into different nickel hydroxide phases, which correlated the composition of Ni-MOF with the OER activity of the derived metastable nickel hydroxide phases.