Air filter comprising an active element and a housing structure comprising an air inlet 12b and an air outlet 14b the active element comprising or consisting of a polymer foam 1 comprising metal particles 2 and an adsorbent material 3. A second aspect relates to a polymer foam 1 comprising metal particles 2 selected from one or any combination of copper, zinc, silver, potassium, selenium, titanium, gold, palladium, platinum which are present as metals, metal compounds, or metal alloys, or any combination thereof, the metal particles present in an amount from greater than about 30 wt% based on the total weight of the filled polymer foam 1 A third aspect relates to a polymer foam 1 comprising or consisting of polyimide comprising metal particles 2. A further aspect relates to a method of making a polymer foam 1 comprising forming a mixture by: i) dissolving a monomer, polymer precursor or polymer in a solvent to form a solution； ii) combining the solution from i) with water to form a blowing agent； and further combining therewith； an isocyanate； a catalyst； a pore former； metal particles 2 and/or an adsorbent 3 and homogenising the mixture.
