A new aluminoborate, [C 5 H 6 N][AlB 12 O 14 (OH) 12 ], has been hydrothermally synthesized at 200°C. The single-crystal diffraction study reveals that it crystallizes in space group C2/c. It consists of aluminoborate clusters [AlB 12 O 14 (OH) 12 ] − and counterions [C 5 H 6 N] + . The aluminoborate cluster contains an Al(OH) 6 octahedron as a core that is capped by two raft-like polyborate units [B 6 O 7 (OH) 6 ]. These clusters are further interlinked by extensive hydrogen bonding to form a three-dimensional (3D) network, containing large channels along the b-axis, in which the [C 5 H 6 N] + cations are located.