A heat storage material comprising mesoporous Mg(OH)2 and having pores loaded with a phase change material is described. The heat storage material has a cooling latent heat of 130-140 J/g, and a solidification enthalpy of 120-135 J/g, and a thermal conductivity of 25-45 W·m−1·K−1. The phase change material may be polyethylene glycol, and the polyethylene glycol does not leak from the pores of the mesoporous Mg(OH)2 when heating or cooling over phase transitions.