Regardless of their individual differences in pore size evolution and absolute surface area, heated Mg-, Ni-and Ni-rich NixCo1-x-struvites preserve mesoporous frameworks. On the other hand, Co-and Co-rich NixCo1-xstruvite eliminate any potential mesoporous structures completely due their fast reconfiguration to crystalline M-dittmarite NH4MPO4•H2O. The amorphization to a stable non-crystalline phase during degassing seems to be necessary to obtain any mesoporous system and probably prevents the collapse of mesopores due to the absence of a crystalline reconfiguration. The high stability of an occurring amorphous phase could have stopped further diffusion of volatiles out of the compound. Since a particular mesoporous framework configuration seems to be directly linked to an element specific amorphous phase, and cannot be predicted a priori from the precursor material, we suggest that the small-angle scattering signal (and the resulting pore size distribution) itself might constitute a fingerprint for a specific amorphous phase. Porous amorphous phases could be classified in such a way. While this idea would have to be fully verified, an indicator for this could be observed in the major differences in the mesoporosity of heated Mg-and Ni-struvite, which in turn are directly connected to the stability and composition of the amorphous phases. By adjusting the reaction conditions (Ni/Co ratio in precursor M-struvite, temperature, humidity) mesoporous materials with different pore structures can be obtained. In such a way, an engineering of the mesoporous framework can be performed for a distinct applicational use e.g. in electrocatalysis. The as-obtained surface area values of the mesoporous struvite-based phosphate materials are comparable to other mesoporous phosphates and their related phosphonates synthesized through much more complex chemical procedures . Transition metal phosphates are frequently used in electrodes or supercapacitors , the same mesoporous analogues would potentially exhibit a higher performance due to enhanced reactivity. A coated or doped amorphous mesoporous transitional metal phosphate might potentially improve properties by exhibiting e.g. high electrocatalytical activity. However, this aspect needs to be further tested. As we suggested in a previous study , M-struvite could be precipitated out of industrial or mining waste waters. Due to its fast precipitation and low solubility product Ksp, it is also occurring as a biomineral in specialized bacteria species . Through a simple thermal treatment, these compounds containing critical raw materials such as phosphate or cobalt could be re-and upcycled for industrial purposes. In summary, we observed three major effects in M-struvite-derived materials which are visualized in Figure : (a) the amorphization and densification of Mg-and Ni-struvite majorly through linking of the PO4 -units with the MO6 -units due to loss of coordinating H2O together with minor NH4,and (b) their formation of isolated micropores and the connection to larger potentially elongated/worm-like mesoporous frameworks. In (c) a complete reconfiguration of X-shaped Co-struvite occurs to crystalline 2D sheet-shaped Co-dittmarite, without the evolution of significant porosity.