Two New 2D POMs‐Based Inorganic‐Organic Hybrid Compounds Constructed from the Proline and 4,4’‐Bipy Mixed Ligands

Two new 2D hybrid compounds derived from Keggin‐type [ BW 12 O 40 ] 5− anion, proline and 4,4’‐bipy were synthesized, namely, [ Co II 2 (proline)(4,4’‐bipy)( H4 ,4’‐bipy) 2 ( OH )( H 2 O ) 2 ][ BW 12 O 40 ]• 3H 2 O ( 1 ) and [ Co II 3 (proline) 2 (4,4’‐ bipy) 2 ( H4 ,4’‐bipy) 4 ( OH ) 2 ( H 2 O ) 4 ][ BW 12 O 40 ] 2 • 6H 2 O ( 2 ). They are characterized by single‐crystal X‐ray diffraction, FT‐IR spectra, powder X‐ray diffraction ( PXRD ), thermogravimetric analyses ( TGA ) and XPS spectra. All compounds represent 2D framework, but the structures possess some distinctions to a certain degree. In compound 1 , 1D wave‐like chains are formed. The chains and polyanions are stacked each other in an ABAB fashion to yield a 2D network. However, compared with compound 1 , compound 2 exhibits the same construction except for the opposite arrangement mode. Moreover, their electrochemical behaviors and fluorescence properties have been investigated. The electrochemical properties show that compounds 1 , 2 display good electrocatalytic activities for the reduction of nitrite.