Sacrificial Synthesis of Supported Ru Single Atoms and Clusters on N-doped Carbon Derived from Covalent Triazine Frameworks: A Charge Modulation Approach.

Zihao Zhang,Ziqi Tian,Pingying Liu,Francis Okejiri,Siyu Yao,Vinayak P Dravid,Sheng Dai,Kun He,Xiaobing Hu,Xiang Zhu,Jie Fu

doi:10.1002/advs.202001493

Abstract

High‐temperature pyrolysis of nitrogen (N)‐rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N‐carbon‐supported metal catalysts. Herein, covalent triazine framework (CTF) and CTF‐I (that is, CTF after charge modulation with iodomethane) are presented as sacrificial templates, for the synthesis of carbon‐supported Ru catalysts—Ru‐CTF‐900 and Ru‐CTF‐I‐900 respectively, following high‐temperature pyrolysis at 900 °C under N2 atmosphere. Predictably, the dispersed Ru on pristine CTF carrier suffered severe sintering of the Ru nanoparticles (NPs) during heat treatment at 900 °C. However, the Ru‐CTF‐I‐900 catalyst is composed of ultra‐small Ru NPs and abundant Ru single atoms which may have resulted from much stronger Ru—N interactions. Through modification of the micro‐environment within the CTF architecture, Ru precursor interacted on charged‐modulated CTF framework shows electrostatic repulsion and steric hindrance, thus contributing toward the high density of single Ru atoms and even smaller Ru NPs after pyrolysis. A Ru—Ru coordination number of only 1.3 is observed in the novel Ru‐CTF‐I‐900 catalyst, which exhibits significantly higher catalytic activity than Ru‐CTF‐900 for transfer hydrogenation of acetophenone.

Highlights

High-temperature pyrolysis of nitrogen (N)-rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N-carbon-supported metal catalysts
The Ru-covalent triazine framework (CTF)-I-900 catalyst is composed of ultra-small Ru NPs and abundant Ru single atoms which may have resulted from much stronger Ru–N interactions
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are important classes of crystalline porous organic architectures that have shown promising potential in different areas of application including gas sorption, energy storage, and conversion, catalysis, etc.[1,2,3]. Because of their high carbon contents and relative stability of the carbon framework, high-temperature carbonization of MOFs or COFs has been identified as a facile synthetic strategy of obtaining highsurface-area porous carbon supports[4,5,6,7] or even various carbon-supported metal nano-catalysts, from MOFs owing to their intrinsic metal-organic hybrid nature.[8,9,10,11]

Summary

Introduction

High-temperature pyrolysis of nitrogen (N)-rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N-carbon-supported metal catalysts. Through modification of the micro-environment within the CTF architecture, Ru precursor interacted on charged-modulated CTF framework shows electrostatic repulsion and steric hindrance, contributing toward the high density of single Ru atoms and even smaller Ru NPs after pyrolysis.

Results

Conclusion