The use of a metathetic catalytic reaction in the degradation of block copolymers is an important opportunity to develop varying porous structures using a one-pot method. In a non-solvent system, the 2nd Generation Grubbs’ catalyst etches alkene containing polymers. The structural integrity of the system is maintained over relatively short time periods. This allows the degradation of the alkene component whilst maintaining the microstructure. Catalytic control leads to porous structures of varying size, density, and distribution. This method is demonstrated on backed thin films, resulting in varying porosities. Pore density and regularity is enhanced by decreasing the film thickness to improve mass transfer of the catalyst through the polymer and increase stability from the supportive backing.