Porous coordination polymer polymorphs with different flexible pores using a structurally flexible and bent 1,3-bis(4-pyridyl)propane ligand.

Porous coordination polymer (PCP) polymorphs with the formula [Cu(CF3SO3)2(bpp)2]n [1 and 2, where bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and crystallographically characterized, and their distinguishable porous properties have been investigated. 1 was obtained by the removal of guest acetone molecules from one-dimensional PCP {[Cu(CF3SO3)(bpp)2]·CF3SO3·2acetone}n (1⊃2acetone), while 2 was derived from two-dimensional PCP {[Cu(CF3SO3)2(bpp)2]·H2O}n (2⊃H2O) by the loss of guest H2O molecules. The desolvated PCPs 1 and 2 with the same formula [Cu(CF3SO3)2(bpp)2] showed distinguishable structures, suggesting PCP polymorphs. In addition, their adsorption behaviors were completely different: 1 showed adsorption with the structural transformation from closed to open forms, while 2 appeared to expand its framework for only as long as was required for the passage of guest molecules. To the best of our knowledge, PCP polymorphs showing either of two different types of flexible pores are very rare.