Quasi-Phthalocyanine Conjugated Covalent Organic Frameworks
with Nitrogen-Coordinated Transition Metal Centers for High-Efficiency
Electrocatalytic Ammonia Synthesis
posted on 2021-12-22, 12:33authored byMinghang Jiang, Linkai Han, Peng Peng, Yi Hu, Yan Xiong, Chunxia Mi, Zuoxiu Tie, Zhonghua Xiang, Zhong Jin
Developing
high-performance nitrogen reduction reaction (NRR) electrocatalysts
is an ongoing challenge. Herein, we report a pyrolysis-free synthetic
method for introducing ordered quasi-phthalocyanine N-coordinated
transition metal (Ti, Cu, or Co) centers into a conjugated two-dimensional
(2D) covalent organic framework (COF) for enhanced NRR performance.
Detailed experiments and characterizations revealed that the NRR activity
of Ti-COF was clearly better than that of Cu-COF and Co-COF, because
of the superior abilities of Ti metal centers in activating inert
N2 molecules and suppressing the hydrogen evolution reaction
(HER). The resulting Ti-COF exhibits a high NH3 yield of
26.89 μg h–1 mg–1cat. and a Faradaic efficiency of 34.62% for NRR. Density functional
theory (DFT) calculations verify that Ti-COF can effectively adsorb
and activate N2 molecules and inhibit HER compared with
Cu-COF, Co-COF, and pristine COF catalysts. This work opens a new
avenue for developing 2D-COF materials that contain abundant coordinated
transition metal centers toward electrocatalytic NRR.