The potential for tailored synthesis of porous materials using catalytic degradation of block copolymers has been shown, employing an adaptable one-pot method. Carefully selected solvent systems help to control the pore size and molecular weight of the product. In the degradation of PS–PB–PS, 2nd Generation Grubbs' catalyst creates scissions in the PB carbon–carbon double bonds resulting in the formation of a porous structure. Critically, methanol is used to maintain the integrity of the polymeric structure during this etching. Catalyst deactivation effected by methanol can be limited through using an excess of 1-hexene; thereby introducing a competitive metathesis process. Altering the ratio of the co-solvents employed further controls the degradation of PS–PB–PS and hence the resulting pore structures.