Robust Th-MOF-Supported Semirigid Single-Metal-Site Catalyst for an Efficient Acidic Oxygen Evolution Reaction

Abstract

Constructing metal−organic framework (MOF) electrocatalysts toward an acidic oxygen evolution reaction (OER) remains a huge challenge owing to the generally poor stability of MOFs during the acidic OER process. Herein, Th-MOF-supported semirigid single-metal-site catalysts of MCl 2 @Th-BPYDC (M = Cu, Co, Ni) were prepared by postmetalation of a bipyridyl Th-MOF (Th-BPYDC) crystal toward an acidic OER. Impressively, the structure of the anchoring single-metal site can be well resolved by single-crystal X-ray diffraction, giving a nearsquare-planar MN 2 Cl 2 coordination geometry, indicative of its potential as a double-accessible open-metal site and an unusual semirigid character because of two rotatable charge-balance Cl − anions. The optimal CoCl 2 @Th-BPYDC not only discloses an outstanding acidic OER activity comparable to commercial IrO 2 but also exhibits a high electrocatalytic stability, which is attributed to the combination of the robust rigid Th-BPYDC framework, the strong chelating coordination between single-metal-site with bipyridine N in BPYDC ligand, and an accessible open single-metal site. More importantly, as unveiled by theoretical calculations and kinetic analysis, the single-metal-site catalysts show an unusual semirigid character during the OER process, totally different from the well-known MN 4 rigid single-site catalysts since Cl atoms are found to rotate freely to provide suitable geometric space when attaching and activating reaction intermediates, thus largely reducing the reaction energy barrier.

Exploration and Application of the Self-Optimization Phenomenon of a Trimetal-Based MOF Electrocatalyst in the Oxygen Evolution Reaction

“…Metal–organic frameworks (MOFs), as a material with the advantages of a high specific surface area, rich pore structure, abundant and diverse components, and well-defined metal centers, have received widespread attention in the field of electrocatalysis. , However, MOFs also have some disadvantages, such as the low conductivity and low mass permeability caused by the inherent insulation of organic ligands, which limits their direct application as an electrocatalyst in OER. − Directly loading MOFs on conductive substrates is a feasible method to improve the conductivity. The conductive substrates can not only significantly improve the conductivity but also provide templates for the growth of MOFs, reducing the agglomeration of MOFs in the growth process. , For example, Chen et al successfully constructed a self-supported NiCoZnP/NC nanosheet array on carbon cloth (CC), avoiding the use of a binder, significantly reducing contact resistance and exhibiting super hydrophilic properties .…”

Recent progress in metal–organic frameworks (MOFs) for electrocatalysis

“…7a and b), which is linked by a Th 6 cluster and a BPYDC ligand. 79 The prepared catalysts all have a well-defined single-crystal structure (Fig. 7c), and the metal sites are near-square planar MN 2 Cl 2 coordination geometries that may become double-channel open metal sites, while two rotatable charge-balanced Cl– anions confer a semi-rigid character (Fig.…”

Engineering defective trimetallic metal–organic framework nanosheets for advanced water oxidation electrocatalysis

“…20,21 On the other hand, the coordinatively unsaturated metal atoms and hydroxide ligands can also serve as active centres to enhance the electrocatalytic performance. 22,23 More importantly, a strong synergistic effect induced by multiple metal active sites can also greatly promote the electrocatalytic performance. 24,25 These advantages have enabled MOFs to be promising materials as electrocatalysts toward the OER.…”