Efficient production of hydrogen from formic acid using a covalent triazine framework supported molecular catalyst

Area of Science:

• Catalysis
• Materials Science
• Green Chemistry

Background:

• Efficient hydrogen production is crucial for renewable energy.
• Current catalysts often suffer from low stability or produce CO impurities.
• Developing robust and selective catalysts for formic acid decomposition is an active research area.

Purpose of the Study:

• To develop a highly active and stable heterogeneous catalyst for hydrogen production from formic acid.
• To investigate the role of the covalent triazine framework (CTF) support in enhancing catalytic performance.
• To achieve high turnover frequencies (TOFs) and turnover numbers (TONs) for sustainable hydrogen generation.

Main Methods:

• Synthesis of a covalent triazine framework (CTF) support using biphenyl and pyridine carbonitrile building blocks.
• Immobilization of an iridium(III) pentamethylcyclopentadienyl [Ir(III)Cp*] complex onto the CTF support.
• Characterization of the catalyst's surface area (BET) and porosity.
• Evaluation of catalytic activity for hydrogen production from formic acid, measuring TOFs and TONs.

Main Results:

• The Ir(III)Cp*-CTF catalyst achieved initial TOFs up to 27,000 h⁻¹ and TONs exceeding one million.
• The CTF support exhibited a high BET surface area (1800 m²/g) and facilitated reactant/product diffusion.
• Pyridinic sites on the CTF activated formic acid, leading to unprecedented hydrogen production rates.
• The catalyst demonstrated air stability, produced CO-free hydrogen, and was fully recyclable.
• High hydrogen production rates (>60 mol/L/h) were achieved at 16 wt% Ir loading.

Conclusions:

• The heterogeneous Ir(III)Cp*-CTF catalyst offers superior performance for formic acid-based hydrogen production.
• The unique properties of the CTF support are key to the catalyst's high activity and stability.
• This catalyst represents a significant advancement towards process intensification for CO-free hydrogen generation.