Cooperative Guest Inclusion by a Zeolite Analogue Coordination Polymer. Sorption Behavior with Gases and Amine and Group 1 Metal Salts

Reaction of CuX2 (X = NO3, Cl, (SO4)1/2) salts and Hpymo·HX (Hpymo = 2-hydroxypyrimidine;
X = Cl, NO3) in aqueous amine solutions (amine = NH3, CH3NH2) leads to formation of the poorly crystalline
three-dimensional open-framework coordination polymer [Cu(pymo-N1,N3)2]∞ (1). Under the same reaction
conditions, but in the presence of amine and group 1 metal salts of single charged voluminous anions, highly
crystalline clathrates of the type {[Cu(pymo-N1,N3)2]·(AX)1/3}∞ (1·AX with A = NH4, CH3NH3, Li, K, Rb;
X = ClO4, BF4, PF6) are obtained. The X-ray crystal structure of 1·NH4ClO4 reveals that the combination of
square-planar Cu2+ ion with 120° bond angles provided by Hpymo generates a three-dimensional porous [Cu(pymo-N1,N3)2]∞ framework with ammonium and perchlorate ions and water molecules included in the pores.
1 possesses a rich host−guest chemistry. Indeed, N2 sorption at 77 K by empty host 1 reveals its microporous
nature with a BET surface area of ca. 200 m2 g-1. Hydrated 1 loses water upon heating and when exposed to
moist air regenerates the original hydrated material. Likewise, 1·NH4ClO4 loses ammonia upon heating, giving
the corresponding activated acidic material 1·HClO4 which upon exposure to gaseous ammonia regenerates
1·NH4ClO4. In addition, 1 reversibly and selectively sorbs AClO4 salts (A = NH4, Li, Na, K, Rb) when
exposed to AClO4 aqueous solutions giving highly crystalline 1·AClO4 clathrates. Cl-, NO3-, SiF62-, and
SO42- salts are, however, not taken up. Salt sorption curves are of type V and possess hysteresis loops. This
behavior agrees with the observed guest-induced structure phase change taking place in the 1 framework after
guest inclusion.