Abstract: The present invention relates to a catalyst washcoat composition comprising a slurry comprising at least one platinum group metal and/or at least one non-platinum group metal supported on at least one support; and at least one pore forming agent having a particle size ranging from 100 nm to 5.0 ?m, wherein the pore forming agent is selected from carbon nano-tubes, carbon nano-fibres, activated carbon, resins, cellulose powder, and polymer spheres. The present invention also provides a catalyst article for capturing particulate matter of size ranging from 1.0 nm to 100 ?m, said article comprising the catalyst washcoat deposited on a substrate and calcined to form pores of which 50%-100% have a pore size ranging from 100 nm to 5.0 ?m.