<p>Activated carbon (AC) modification via liquid-phase impregnation is widely implemented and used for indoor formaldehyde removal, with a focus on the adsorption capacity and efficiency of the modification. In this study, AC was first pretreated under negative pressure and then impregnated with a 4-amino-1,2-butanediol (ABDO) solution. Elemental analysis, porous texture characterization, SEM analysis, adsorption capacity measurements, and measurements of isotherms and kinetic modeling were conducted. The adsorption isotherms conformed to both the Langmuir and Freundlich models, whereas the adsorption kinetics were consistent with the pseudo-second-order model, with <i>R</i>² values greater than 0.99. Multilinear plots of the adsorption stage were generated by fitting the intraparticle model. Quantitative analysis and mathematical modeling revealed that negative pressure pretreatment of AC enhanced both the adsorption capacity and efficacy of ABDO, with the maximum equilibrium capacity reaching 259.18&#xa0;mg·g⁻¹, which was 2.1% greater than that of untreated AC. Additionally, negative pressure pretreatment of AC and initial concentrations of ABDO synergistically increased the adsorption capacity and efficiency, significantly increasing the adsorption capacity at 0.011&#xa0;MPa and 127.5&#xa0;g·L⁻¹. However, the enhancement effects diminished at an initial concentration of 170.0&#xa0;g·L⁻¹. The pressure and concentration gradients were the main driving forces for enhancing the adsorption capacity and efficiency. The subsequent decrease in the enhancement is attributed to the high initial ABDO concentration mitigating capillary condensation in the AC pores, blocking micropores and preventing further ABDO molecules from accessing interior adsorption sites.</p> Graphical Abstract <p></p>