Automotive suspension systems are important parts of vehicles and are vital for ride comfort, safety, and handling stability. Various active and semi-active suspension configurations have been developed and applied to high-end cars, but passive suspensions are still the most widely used type because of their lower cost, higher reliability, simpler structure, and lack of energy consumption. Consequently, it is meaningful to study a novel passive suspension based on a hydrophobic microporous material, whose working mechanism is illustrated using the Laplace capillary principle. A stiffness model is built based on hydrostatic principles, the primary resonance response of the nonlinear dynamic system is established using averaging, the performance of the passive suspension is simulated using MATLAB Simulink, and the ride comfort is assessed based on the weighted root-mean-square acceleration. The results show that the natural frequency, suspension deflection, and weighted root-mean-square acceleration of the new suspension meet the design objectives. In addition, for a given natural frequency, the suspension deflection of the studied suspension is less than that of a linear suspension, and the proposed low-pressure molecular-spring suspension offers a new choice when designing passive automotive suspensions.