Coordination engineering in single-atom covalent organic framework photocatalysts for solar-driven nitrogen fixation

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• Single-atom catalysts integrated into covalent organic frameworks (COFs) offer a tunable platform for photocatalytic nitrogen reduction.
• Understanding the structure-activity relationships in these catalysts is crucial for optimizing nitrogen fixation.

Purpose of the Study:

• To investigate the mechanistic interplay between local coordination environments and catalytic performance in metal-phthalocyanine-like single-atom catalysts (TM@pdiCOF).
• To explore the impact of ligand N-doping on catalytic efficiency and photophysical properties for solar-driven nitrogen fixation.

Main Methods:

• Spin-polarized density functional theory (DFT) calculations were employed.
• Analysis of charge transfer and metal-N2 interactions using -pCOHP/ICOHP.
• Thermodynamic profiling using the computational hydrogen electrode (CHE) framework.

Main Results:

• Side-on N2 adsorption was identified as key for superior activation via enhanced charge transfer.
• The initial protonation step was determined as the potential-limiting step.
• N-doping systematically tuned metal environments, lowering limiting potentials and suppressing hydrogen evolution.
• Optimized catalysts achieved competitive limiting potentials: -0.59 V (Fe), -0.42 V (Co), and -0.76 V (Ni).
• Heteroatom doping improved visible-light harvesting through spectral blue shifts and band-gap narrowing.

Conclusions:

• Ligand modulation via N-doping is an effective strategy to optimize both reaction energetics and optical properties.
• This approach facilitates efficient solar-driven nitrogen fixation using single-atom COFs.
• The findings provide a robust design principle for developing advanced photocatalysts.