A method for controlling pore size of a membrane that includes providing a porous magnetic architecture and magnetizing the porous magnetic architecture. The porous magnetic architecture changes pore size when magnetized. A method for inhibiting the mobility of a solute through a membrane includes magnetizing a porous magnetic architecture in a flow stream that includes a solute. A membrane system for a solute includes a porous magnetic architecture disposed within a flow stream that also includes a solute, and a magnetic source disposed such that the nonuniform porous magnetic architecture is selectively magnetized.