Synergistic Physisorption-Chemisorption Mechanism Enables High-Capacity NO₂ Capture in Nitrogen-Rich Conjugated...

Area of Science:

• Materials Science
• Polymer Chemistry
• Chemical Engineering

Background:

• Small-molecule stabilizers for nitrocellulose (NC) have limited active sites, hindering autocatalytic reaction inhibition in complex environments.
• Conjugated microporous polymers (CMPs) offer high thermal stability and abundant active sites, presenting a promising alternative for NC stabilization under demanding conditions.

Purpose of the Study:

• To synthesize and evaluate N-rich CMPs as novel stabilizers for nitrocellulose (NC).
• To investigate the stabilization mechanism and gas adsorption capabilities of the developed CMPs.

Main Methods:

• Synthesis of 3D polyamine (PTPA) networks via Buchwald-Hartwig (BH) coupling.
• Characterization of PTPA-2's porous structure, specific surface area, and thermal stability.
• Evaluation of PTPA-2's performance in vacuum stability tests (VST) and NOₓ titration tests.
• Analysis of NC decomposition products using TG-DSC-FTIR-GC-MS.
• Density functional theory (DFT) simulations to elucidate adsorption mechanisms.

Main Results:

• PTPA-2 exhibited a high specific surface area (700 m²·g⁻¹) and excellent thermal stability.
• 3% PTPA-2 reduced NC outgassing by 58% in VST and doubled the time to color change.
• PTPA-2 adsorbed NOₓ gas (8.05 × 10⁻² mmol/g) and restrained NC's NOₓ release by 60%.
• PTPA-2 stabilized NC by absorbing NO₂ through coordinated processes involving physical adsorption and chemical immobilization at -N-Ar-NH- sites.

Conclusions:

• N-rich CMPs, specifically PTPA-2, are effective stabilizers for nitrocellulose, offering high NOₓ adsorption capacity and stability.
• The findings provide a pathway for designing advanced stabilizers and inspire the use of porous materials for exhaust gas adsorption.