Disclosed are adsorbent materials that comprise a porous material having a continuous silica phase coated with a carbon layer, and a water-insoluble precipitate comprising a metal cation and an anion disposed substantially evenly throughout the adsorbent material. In some examples, the plurality of pores can have an average characteristic dimension of from 0.1 Å to 100 Å. The water-insoluble precipitate can be formed in the plurality of pores of the porous material by contacting the porous material with a first aqueous solution comprising a metal cation and contacting the porous material with a second aqueous solution comprising an anion wherein the metal cation and the anion combine to form the water-insoluble precipitate in the plurality of pores of the porous material, thereby forming the adsorbent material.
