A Crystalline Mesoporous Germanate with 48-Ring Channels for CO₂ Separation

One of the challenges in materials science has been to prepare crystalline inorganic compounds with mesopores. Although several design strategies have been developed to address the challenge, expansion of pore sizes in inorganic materials is more difficult compared to that for metal-organic frameworks. Herein, we designed a novel mesoporous germanate PKU-17 with 3D 48×16×16-ring channels by introducing two large building units (Ge₁₀ and Ge₇ clusters) into the same framework. The key for this design strategy is the selection of 2-propanolamine (MIPA), which serves as the terminal species to promote the crystallization of Ge₇ clusters. Moreover, it is responsible for the coexistence of Ge₁₀ and Ge₇ clusters. To our knowledge, the discovery of PKU-17 sets a new record in pore sizes among germanates. It is also the first germanate that exhibits a good selectivity toward CO₂ over N₂ and CH₄.