Gasoline particulate filter

A catalytic wall-flow monolith for use in an emission treatment systemcomprises a porous substrate and a three-way catalyst (TWC), wherein the TWC is distributed substantially throughout the porous substrate and wherein the TWC comprises: (i) alumina; (ii) one or more platinum group metals; and (iii) an oxygen storage component (OSC), wherein the OSC comprises ceria or one or more mixed oxides comprising cerium and is present in a ratio by weight of OSC to alumina of from 65:35 to 85:15