Nanoporous metal foam gas and fluid filters

A method of constructing a free-standing metal foam, the method comprising:

• electrochemically depositing a selected metal into one or more nanoporous templates to form metal nanowires employing a first electrolyte solution containing the selected metal;
• dissolving the one or more nanoporous templates in a selected solution;
• replacing some or all of the selected solution with water to produce a nanowire/water suspension;
• freezing the nanowire/water suspension into a frozen nanowire/ice mixture;
• sublimating the ice portion of the frozen nanowire/ice mixture to produce the free-standing metal foam comprising a plurality of nanowires, wherein the free-standing metal foam comprises an open-cell structure;
• and
• further electrochemically depositing more of the selected metal upon and throughout the free-standing metal foam, using a second electrolyte solution including one or more leveling agents in a homogeneous manner so as to contiguously coat the plurality of nanowires of the free-standing metal foam, thereby increasing a nanowire diameter of each of the plurality of nanowires and intersection areas of the free-standing metal foam from interior surfaces to exterior surfaces of the free-standing metal foam, and forming a plurality of nucleation-derived granular surface features having sizes between approximately 0.1 μm and 5 μm, resulting in thickening of the free-standing metal foam around individual nanowires of the plurality of nanowires, as well as at intersections of multiple nanowires of the plurality of nanowires, wherein a contact area at the intersections is increased by over an order of magnitude, thereby forming a mechanically reinforced three-dimensional scaffold that exhibits enhanced mechanical stability and enables the free-standing metal foam to have a yield strength of at least 1 kg load over 120 mg of the free-standing metal foam while retaining an open porous structure with a tunable density from 1% to 30% of bulk density.