Aluminoborate‐Based Molecular Sieves with 18‐Octahedral‐Atom Tunnels

A framework of AlO6 octahedra is present in the microporous aluminoborate HAl3B6O12(OH)4 (PKU-1; see picture), which was synthesized from AlCl3 in a boric acid flux. The octahedra share two or three edges with neighboring octahedra to form a framework with 18-ring tunnels along [001] and 10-ring tunnels along {100}. The borate groups share vertices with the octahedra, compensating the negative charge of the octahedral framework and almost completely blocking the 10-ring channels.