We present a template-free synthesis method for amorphous and mesoporous TMPs through a simple thermal treatment of a crystalline precursor called M-struvite NH4MPO4•6H2O (Figure ). In M-struvite M 2+ is usually Mg 2+ , but other divalent cations such as Ni , or Co , can easily substitute Mg 2+ in the struvite structure due to similar ionic radii (where other examples considered elsewhere include among others Zn 2+ , Fe 2+ , Mn 2+ ) . In our recent study, we showed how to precipitate and engineer Ni-and Co-struvites crystals from aqueous solutions and we explored their phase diagrams and growth mechanisms . Importantly, it has been also recently shown that common Mg-struvite converts directly to amorphous regular mesostructured frameworks of high surface area (~300 m 2 /g) by thermal heating. Such thermal composition method has not been used so far to prepare mesostructured TMPs containing Ni and Co. In this study we show how the mesoporous metal phosphate compounds systematically differ in their absolute surface, pore size distribution and temporal evolution from each other although they share the same original isostructural precursor struvite. A direct relationship between amorphicity and mesoporosity is demonstrated. Our findings show that the evolution of mesoporosity is not just a simple case of degassing of ammonia and water from the crystal, but in involves complex restructuring of amorphous solids. By adjusting the reaction conditions, a high degree of control over the formed porous structure is achieved, which is relevant for a customized applicational use e.g. in electrocatalysis.