The removal characteristics of sub-25 nm ultrafine particles (UFPs) by different porous nanomaterials with different morphologies were studied based on efficiency curves obtained with specially designed filtration system. The material morphological effects on UFPs collection were investigated. The results demonstrate a complex and synergic mechanism of material structural framework, pore size distribution, and porosity order in terms of diffusion and interception dependent on flow velocity. Both porosity and fiber-like tubular structures promoted the UFPs removal. Microporosity and disordered mesoporosity could enhance the roughness of the internal surface and intensify the interaction with UFPs. Specifically, the large and ordered mesoporosity was able to render selectivity for UFPs at certain sizes and exhibited the best particle collection performance which can be largely associated with significant pore size and volume. The dependence of the ratio of diffusion to interception on flow velocity and the comparison of different pores in terms of the matching sizes with particles derived from single sphere efficiency model fitting results were also discussed. This work is significant to deeper understanding of interactions between airborne nanoparticles and porous surfaces. (C) 2018 Published by Elsevier B.V.