Clearly, a direct correlation between the amorphicity and mesoporosity of the material exists as only the amorphous compounds were also mesoporous. This correlation starkly demonstrated itself in heated NixCo1-x-struvite mixtures, where Ni# ≥ 50% all showed BET surface areas of around 80-90 m²/g and average pore sizes of 4 nm with type IV hysteresis loops similar to Ni-struvite (ESI: Figure , Table ). Below Ni# ≤ 50%, the BET surface area decreased to 20-30 m²/g while the average pore size increased rapidly from 3-4 nm to tens of nanometers. The heated Co-rich NixCo1-x-struvite and pure Co-struvite demonstrated no significant mesoporosity and low surface area (1.1 m²/g), indicated by type II isotherms (ESI: Figure , Table ). All summarized BET data, additional adsorption/desorption pore size distributions and isotherms of M-struvite can be found in the ESI (ESI: Figure and S6, Table and S4).