Pore Geometry-Driven Capture of Trace Aromatic Volatile Organic Compounds in Al-Based MOFs.

Abstract

Aromatic volatile organic compounds (VOCs) are toxic air pollutants that pose serious health risks even at trace concentrations. Their nonpolar character makes the design of efficient sorbents particularly challenging, as adsorption is governed mainly by weak dispersion forces. Here, we identify pore geometry as an effective structural descriptor for discovering metal-organic frameworks (MOFs) capable of efficient trace-level VOC capture. Screening a diverse set of MOFs revealed that one-dimensional channels with rhombic or square cross sections enhance host-guest interactions and promote strong affinity for aromatic molecules. Guided by this principle and sustainability-by-design criteria, we identify MIP-211(Al) (Materials from the Institute of Porous Materials of Paris) as a top performer with among the highest toluene uptake of 4.7 mmol g^-1 at 0.0008 <i>P</i>/<i>P</i>₀ (31 ppm). This material combines excellent cycling stability, facile regeneration under vacuum, and scalable green synthesis. Synchrotron powder X-ray diffraction (SPXRD) and density functional theory (DFT) calculations confirm that rhombic pore geometry governs strong toluene affinity at trace amounts. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy showed that MIP-211(Al) retains 60% of its performance up to 15% relative humidity. Applying pore geometry as a descriptor in a secondary screening identified a candidate with a toluene uptake of 3.6 mmol g^-1 at 0.0008 <i>P</i>/<i>P</i>₀ (31 ppm) at dry conditions, with potential applicability up to 70% relative humidity. This study demonstrates the importance of pore geometry as a nanoscale parameter for efficient trace aromatic VOC adsorption.