Structural diversity, single-crystal to single-crystal transformation and photocatalytic properties of Cu(II)-metal-organic frameworks based on 1,4-phenylenedipropionic acid

Abstract A series of four new copper(II) based metal-organic frameworks containing 1,4-phenylenedipropionic acid and different N,N′ -donor coligands, namely, [Cu(ppa)(bpy)] n ( 1 ), {[Cu(ppa)(azp)(H 2 O)](H 2 O)} n ( 2 ), {[Cu(ppa)(tdp)(H 2 O)](H 2 O) 2 } n ( 3 ), and {[Cu(ppa)(tdp)](H 2 O)} n ( 4 ), (H 2 ppa = 1,4-phenylenedipropionic acid, bpy = 4,4′-bipyridine, azp = 4,4′-azobipyridine, tdp = 4,4′-thiodipyridine) have been successfully synthesized and structurally characterized by elemental analysis, IR, UV–vis, TGA, XRPD and single-crystal X-ray diffraction. Compound 1 containing a short and rigid bpy coligand displays a 2D square lattice ( sql ) topology while 2 and 3 which contain more flexible and longer azp and tdp coligands possess two-fold interpenetrating diamond-like ( dia ) 3D framework. Finally, the thermal-induced compound 4 is transformed from compound 3 by heating, through single-crystal-to-single-crystal transformation, adopting a CdSO 4 -like ( cds ) 3D framework. Additionally, the solid stated compounds 1 – 4 exhibit the energy band gaps of 3.50, 3.16, 3.53 and 3.31 eV, respectively. Thus, the photocatalytic properties of 1 – 4 have been investigated. Approximately 84.9% for 1 , 93.3% for 2 , 82.0% for 3 and 85.4% for 4 of methylene blue were decomposed within 105 min.