Extending the Pore Size of Crystalline Metal Phosphonates toward the Mesoporous Regime by Isoreticular Synthesis

Crystalline microporous cobalt and nickel bisphosphonates with a hexagonal array of one-dimensional channels 1.8 nm in diameter have been prepared hydrothermally and provide the first example of the use of isoreticular chemistry in the synthesis of phosphonate metal−organic frameworks. The materials contain both physisorbed and coordinating water molecules in the as-prepared form, but these can be removed to give permanent extra-large microporosity, with pore volumes of up to 0.68 cm3 g−1, and coordinatively unsaturated sites, with concentrations up to 4.25 mmol g−1.