Computational Screening of MOFs and Zeolites for Direct Air Capture of Carbon Dioxide under Humid Conditions

With rising CO2 levels, it is important to develop new methods to capture CO2 directly from air. Currently, most direct air capture (DAC) adsorbents, such as amines, rely on chemisorption. However, finding materials with weaker, reversible adsorption could improve the regenerability of these adsorbents. The low concentration of CO2 relative to other components of air and the presence of humidity limit the effectiveness of physisorbent materials for DAC. In this work, we screened the 2014 computation-ready, experimental metal–organic framework (CoRE MOF) database along with silica zeolites, aluminophosphate (AlPO) zeolites, and gallophosphate (GaPO) zeolites for DAC under humid conditions based on heat of adsorption criteria. After the initial assessment, AlPO and GaPO zeolites appeared to be promising adsorbents for DAC. To assess the accuracy of these initial predictions, we compared adsorbate–adsorbent interaction energies predicted by the force field used in screening (UFF) and dispersion-corrected density functional theory. To improve the accuracy of these predictions, first-principles force fields were fit for AlPO and GaPO zeolites. More accurate CO2 and H2O heats of adsorption and adsorption isotherms were computed and showed that AlPO and GaPO zeolites are not suitable for DAC applications.随着二氧化碳（CO₂）浓度持续升高，开发可直接从空气中捕集CO₂的新型方法具有重要意义。目前，多数直接空气捕获（direct air capture, DAC）吸附剂（如胺类材料）均依赖化学吸附机制。然而，研发吸附作用更温和、具备可逆吸附特性的材料，可有效提升这类吸附剂的再生性能。空气中CO₂的浓度远低于其他组分，且存在水汽，这两大因素限制了物理吸附剂应用于DAC的实际效果。本研究基于吸附热判据，针对潮湿环境下的DAC应用场景，筛选了2014版计算就绪实验金属有机框架（computation-ready experimental metal–organic framework, CoRE MOF）数据库，以及硅沸石、磷酸铝（aluminophosphate, AlPO）沸石与磷酸镓（gallophosphate, GaPO）沸石。初步评估结果显示，AlPO与GaPO沸石是颇具潜力的DAC吸附候选材料。为验证该初步预测的准确性，本研究对比了筛选流程中所用通用力场（UFF）与色散校正密度泛函理论所预测的吸附质-吸附剂相互作用能。为进一步提升预测精度，我们针对AlPO与GaPO沸石拟合得到了第一性原理力场。通过计算更精准的CO₂与H₂O吸附热及吸附等温线，结果表明AlPO与GaPO沸石并不适用于DAC应用。