Polymeric organo–magnesium complex for room temperature hydrogen physisorption

Abstract

We report a facile synthesis of a polymeric organo–magnesium complex (MTF–Mg) by reacting Mg-modified-melamine with terephthalaldehyde for room temperature hydrogen physisorption. The pre-modification of melamine allows incorporation of exposed magnesium sites into the complex. The synthesized MTF–Mg complex exhibits a moderate BET surface area up to 137 m² g⁻¹ and a Langmuir surface area up to 222 m² g⁻¹. In this complex, magnesium metal sites act as the active sites for molecular hydrogen adsorption via an electrostatic interaction. The material shows a high isosteric heat of adsorption up to 12 kJ mol⁻¹ and a maximum excess hydrogen uptake up to 0.8 wt% at 298 K and 100 atm, comparable to the values of high surface area MOFs with exposed metals sites under similar conditions. The role of the exposed metal sites in enhancing hydrogen uptake capacity and isosteric heat of adsorption is demonstrated experimentally.