Humid-air competitive adsorption invalidates conventional sorbent screening criteria for direct air capture

Direct air capture (DAC) of CO₂ using solid sorbents is a key negative-emissions technology, but current systems require 5–10 GJ t⁻¹ of thermal energy for sorbent regeneration, which far exceeds the thermodynamic minimum.
High-throughput computational screening of metal organic frameworks (MOFs) offers a route to identifying lower-energy sorbents, yet most screening workflows rely on molecular descriptors evaluated under idealised conditions. These descriptors do not encode the competitive, path-integrated thermodynamics of a full adsorption–desorption cycle under humid air, where co-adsorbed water dominates the energy penalty.
Whether explicitly modelling nonlinear competitive CO₂/H₂O adsorption yields fundamentally different material rankings from conventional linear screening remains untested at database scale. Here we show, by screening 7906 CoRE-MOF-2019 structures through a proxy temperature-vacuum swing adsorption cycle coupled with binary Langmuir-IAST, that nonlinear competitive adsorption changes DAC screening outcomes: all 50 top-performing sorbents (regeneration energy 92-150 kJ mol⁻¹ CO₂) belong exclusively to the nonlinear regime and would be systematically excluded by a linear Henry-regime model.
These top performers cluster at isosteric heats of 43-55 kJ mol⁻¹, partially below the widely applied 50 kJ mol⁻¹ threshold, indicating that this conventional criterion is overly restrictive. CO₂ working capacity emerges as the single most informative predictor of regeneration energy (Spearman ρ = −0.86), while DFT interaction energies show negligible correlation.
These findings provide a quantitative basis for a tiered screening strategy that bridges molecular descriptors and process performance and demonstrate that linear screening models structurally miss the lowest-energy DAC sorbents.