Surface-Modified Ultrathin Metal–Organic Framework Nanosheets as a Single-Site Iron Electrocatalyst for Oxygen Evolution Reaction

Abstract

The development of heterogeneous catalyst with well-dispersed active metal sites is one of the hottest research topics. By properly choosing or designing the host material to stabilize the active sites, host-engineering strategy is commonly applied for the preparation of quasimolecular heterogeneous catalysts. Here, by doping the metal−organic framework (MOF) Co-BPDC with 4-(4′-formylphenyl)benzoic acid, ultrathin nanosheets with an aldehyde group-modified surface were facially produced. Upon the addition of ethylenediamine, the surface aldehyde group was converted into imine groups in situ. At this stage, the Co-BPDC nanosheet still had relatively poor catalytic activity in oxygen evolution reaction (OER). After metalation with Fe 3+ under ambient conditions, the catalytic activity was greatly enhanced for the resulting nanosheet. With a surface Fe content of 2.87 wt %, the observed electrochemical overpotential and Tafel slope for the Co-BPDC nanosheet in OER decreased to 291 mV and 38 mV/decade, respectively. Meanwhile, the nanosheet catalyst also showed moderate catalytic stability. By taking advantage of the ultrathin nanosheet, the catalytic active Fe sites were immobilized on the nanosheet by the surface imine ligands. This strategy enables the economical and facial production of an atomically dispersed metal catalyst in a large scale under ambient conditions. With the easily accessible and modifiable large surface, the ultrathin MOF nanosheet is an ideal host material for anchoring active metal sites after surface modification.

Atomically Dispersed NiNx Site with High Oxygen Electrocatalysis Performance Facilely Produced via a Surface Immobilization Strategy

“…Porphyrin FeN 4 sites can be implanted into graphene to produce active catalysts by ball milling at room temperature . We also illustrated that the postcoordinated surface MN x sites, , as well as surface immobilized MN x sites, have good electrocatalysis activity. , It is reasonable to suppose that the active MN x site can be produced not only by trapping metal atoms with vacancy defects at very high temperatures but also by anchoring the MN x sites on the substrate surface via organic reactions under very mild conditions. By covalently immobilizing the preorganized MN x complex on the substrate surface, atomically dispersed active MN x sites possibly can be prepared in a predictive and scalable way.…”

Surface immobilization of nitrogen-coordinated iron atoms: a facile and efficient strategy toward MNC sites with superior catalytic activities

“…For example, MN 4 sites can be introduced into graphene by ball-milling at room temperature, 37 or directly thermal condensed from the Fe(phen) x complex on the MgO surface at 600 °C; 38 at 250–300 °C, the atomic layer deposition (ALD) of the organometallic complex on the N-doped carbon substrate is an useful preparation strategy for active MN 4 site. 33,39 We also illustrate the successful immobilization of active NiN x 40,41 or FeN x 42 sites on ultra-thin nanosheets at 350 °C or room temperature. Generally, organic covalent bonds can be constructed under very mild conditions.…”

Surface-Immobilized ZnNx Sites as High-Performance Catalysts for Continuous Flow Knoevenagel Condensation in Water

“…Recently, the atomically dispersed MNC (metal–nitrogen-carbon)-type catalysts have emerged as promising alternatives to overcome the drawbacks associated with the high cost of noble metal catalysts. They have demonstrated high performance in various catalytic reactions. − However, a significant limitation has been the tendency of metal atoms to aggregate and form metal nanoparticles under high-temperature preparation conditions, due to their high surface energy. To mitigate this issue, the catalysts usually were prepared with a low metal content, and any formed metal particles are subsequently removed by acid treatment during postprocessing.…”