Ionic liquids and eutectic mixtures as solvent and template in synthesis of zeolite analogues

The challenges associated with synthesizing porous materials(1) mean that new classes of zeolites (zeotypes)-such as aluminosilicate zeolites(2,3) and zeolite analogues(4)-together with new methods of preparing known zeotypes(5), continue to be of great importance. Normally these materials are prepared hydrothermally with water as the solvent in a sealed autoclave under autogenous pressure(6). The reaction mixture usually includes an organic template or 'structure-directing agent' that guides the synthesis pathway towards particular structures. Here we report the preparation of aluminophosphate zeolite analogues by using ionic liquids(7) and eutectic mixtures(8). An imidazolium-based ionic liquid acts as both solvent and template, leading to four zeotype frameworks under different experimental conditions. The structural characteristics of the materials can be traced back to the solvent chemistry used. Because of the vanishingly low vapour pressure of ionic liquids, synthesis takes place at ambient pressure, eliminating safety concerns associated with high hydrothermal pressures. The ionic liquid can also be recycled for further use. A choline chloride/urea eutectic mixture(8) is also used in the preparation of a new zeotype framework.