Magnesium bicarbonate exists only in aqueous solution. Magnesium does not form solid bicarbonate as does lithium. To produce it, a suspension of magnesium hydroxide is treated with pressurized carbon dioxide, producing a solution of magnesium bicarbonate:[1]
Mg(OH)2 + 2 CO2 → Mg(HCO3)2
Drying the resulting solution causes the magnesium bicarbonate to decompose, yielding magnesium carbonate, carbon dioxide, and water: