Gas adsorption and structural diversity in a family of Cu(II) pyridyl-isophthalate metal-organic framework materials.

A family of Cu(II)-based metal-organic frameworks (MOFs) has been synthesized using three pyridyl-isophthalate ligands, HL (4'-(pyridin-4-yl)biphenyl-3,5-dicarboxylic acid), HL (4''-(pyridin-4-yl)-1,1':4',1''-terphenyl-3,5-dicarboxylic acid) and HL (5-[4-(pyridin-4-yl)naphthalen-1-yl]benzene-1,3-dicarboxylic acid). Although in each case the pyridyl-isophthalate ligands adopt the same pseudo-octahedral [Cu(OCR)N] paddlewheel coordination modes, the resulting frameworks are structurally diverse, particularly in the case of the complex of Cu(II) with HL, which leads to three distinct supramolecular isomers, each derived from Kagomé and square nets. In contrast to [Cu(L)] and the isomers of [Cu(L)], [Cu(L)] exhibits permanent porosity. Thus, the gas adsorption properties of [Cu(L)] were investigated with N, CO and H, and the material exhibits an isosteric heat of adsorption competitive with leading MOF sorbents for CO [Cu(L)] displays high H adsorption, with the density in the pores approaching that of liquid HThis article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.