Facile Synthesis of Ultramicroporous Organic-Linked Zincophosphate with High Thermal, Chemical and Water Stabilities

The application of ultramicroporous materials for CO₂ separation is limited by the rarity of materials exhibiting stability and rapid scale-up characteristics. In this study, we propose a rational approach to enhance the structural stability and durability of the pillared layer structure. Through the topotactic replacement of protons with metal ions in the parent 4,4′-bipyridine (bpy)-pillared zincophosphate, we observed the formation of edge-sharing dimers of ZnO₄N and PO₄, as well as the insertion of (VOH₂O)²⁺ into the zinc phosphate layers. This resulted in the modified bpy-pillared bimetal phosphate, [(VOH₂O)(ZnPO₄)₂(bpy)]⋅4H₂O (denoted as NTHU-16 or VZn-bpy-w), which exhibits exceptional structural stability in a wide pH range (pH 2-12) and boiling water. Additionally, a rapid scale-up process reduced the synthesis time of VZn-bpy-w from 48 hours to just 3 hours, significantly increasing efficiency. The vanadyl groups, with easily displaced coordinated water, enhance the strength of the inorganic sheets and create available metal sites for the adsorption and separation of CO₂. This combined strategy of structural enhancement and rapid synthesis offers a new pathway for engineering stable, porous metal phosphates and designing novel organic-inorganic hybrid materials with potential applications in CO₂ separation.