Surfactant-templated mesoporous silicates and mesoporous layered silicate clays having certain porosity parameters are used as reinforcing agents for polymers to make composites. The combination of porosity parameters that allows mesoporous silicates to be competitive with organoclays for the reinforcement of engineering polymers include an average mesopore size of at least 2 nm, a surface are of more than about 50 square meters per gram, a total pore volume of more than about 0.33 cubic centimeters per gram, wherein at least 20% of the total pore volume is due to mesopores about 2 to about 50 nm.