Metal-containing sorbent materials are provided, methods of making the metal-containing sorbent materials, methods of using the metal-containing sorbent materials, and metal complex-containing composite materials resulting from the sorption of basic, nitrogen-containing compounds on the metal-containing sorbent materials are provided. The sorbent materials are prepared by incorporating divalent metals into a precursor material that is formed by treating a porous siliceous material having mesopores with a silane or disilazane surface treatment agent. The metal-containing sorbent materials can be used to capture basic, nitrogen-containing compounds having a molecular weight no greater than 150 grams/mole.