RbCuPO₄-A maximum copper tetrahedral framework adopting the zeotype ABW structure

The sky blue RbCuPO4-ABW is the first reported maximum copper (framework ratio 1∶1) zeotype framework, consisting of alternating PO4 and flattened CuO4 (Cu–O 1.89–1.95 Å) tetrahedra; a second metastable very pale green–blue phase can also be produced by quenching, with conversion to the purely four-coordinate copper material accomplished by application of slight mechanical pressure.