From K[ZnBP₂O₈] to K[(Zn_0.5Al_0.5)₂P₂O₈]: Substitution-Induced Microporous Zincoaluminophosphate with a Congruent-Melting Behavior

An open-frame aluminophosphate, K­[(Zn_0.5Al_0.5)₂P₂O₈] (KZAPO), was rationally designed by a substitution design strategy and synthesized by a high-temperature molten salt method. Compared with the parent crystal of K­[ZnBP₂O₈], KZAPO was characterized by similar 4 × 8 × 8 networks, a comparable short-wave ultraviolet transparency and a more regular tetrahedral frame with the mixing of (ZnO₄)^6– and (AlO₄)^5– anionic groups, highlighting the multifunctional roles that anionic group mixing played in structural and property modulations. In particular, KZAPO was characterized by a high thermal stability (over 850 °C) and a congruent-melting behavior, being conducive to practical applications.