A 3,4-connected beryllium phosphite framework containing 24-ring channels with a very low density.

A new three-dimensional open-framework beryllium phosphite with honeycomb-like channels has been prepared under solvothermal conditions. The alternation of a 24-ring window and a 30-ring window along its extra-large channel is unprecedented in open-framework materials. The compound has a very low density of 1.369 g cm(-3) by integrating an extra-large-pore, interrupted 3,4-connected framework and lightweight beryllium metal in its crystalline structure.