A new mixed-ligand copper pentaborate with square-like, rectangle-like and ellipse-like channels formed via hydrogen bonds

► A new mixed ligands copper pentaborate are synthesised and well characterized. ► The square-like channels and the rectangle-like channels are formed along the c-axis. ► Each square channel is surrounded by four rectangular channels, and vice versa. ► The ellipse-like 16-membered boron rings are formed along the a-axis. ► The ellipse-like channels are the largest channel in the pentaborates reported so far.