Interaction mechanisms of POSS-based adsorbents with VOCs, CO2, CH4, and H2O: theoretical insights and prediction method

The dual nature of Polyhedral Oligomeric Silsesquioxane (POSS), with its cage framework and substituent groups, enables diverse interactions with liquid and gaseous pollutants. While Quantum Mechanical (QM) methods have been used for simpler POSS variants, evaluating all possible combinations of cages and substituents remains impractical. This study aims to fill the knowledge gap on how the polarity of liquid pollutants and the structural features of POSS influence the efficiency of separating Volatile Organic Compounds (VOCs) from aqueous streams in wastewater treatment processes. Using a comprehensive dataset on liquid-liquid adsorption selectivities, we developed a predictive model for estimating VOC-VOC and VOC-water partition coefficients across 1.424 × 10 7 POSS variants, achieving accuracy comparable to expensive QM methods. This model enables users to design novel POSS molecules tailored for wastewater treatment or VOC recovery quickly and efficiently. We explored adsorption mechanisms for CO 2 , H 2 O, and CH 4 , focusing on interactions between the cage and adsorbates, as well as between substituents and adsorbates. Our findings highlight that substituents are crucial for gas adsorption, with their electrostatic properties being a significant factor. While all substituents exhibited strong CO 2 /CH 4 selectivity, this selectivity diminishes in the presence of H 2 O. Additionally, gaseous pollutants are only effectively encapsulated when the POSS cage size exceeds T 10 . This work provides a framework for designing optimized POSS materials for specific separation applications, facilitating the efficient selection of structures for targeted gas and liquid capture. • A large-scale predictive model was developed to accelerate the design of novel POSS nano-adsorbents. • The model predicts liquid separation selectivity that aligns with predictions from quantum mechanical methods. • POSS substituents are more influential in liquid and gas adsorption than the cage. • Interaction sites and strengths between the POSS cage, substituents, and CO 2 , CH 4 , and H 2 O are elucidated.