Synthesis, Structures, and Sorption Properties of Two New Metal–Organic Frameworks Constructed by the Polycarboxylate Ligand Derived from Cyclotriphosphazene

Solvothermal reactions
of hexakis­(4-carboxyphenoxy)­cyclotriphospazene
(H6L1) with copper ions in DMF/H2O produced
one complex, {[Cu6(L1)2(OH)­(H2O)3]·guest}n (1), but with copper ions and auxiliary rigid 4,4-bipyridine (bpy)
produced another new complex, namely, {[Cu3(L1)­(bpy)­(H2O)6]·guest}n (2). These complexes had been characterized by IR spectroscopy,
elemental analysis, and X-ray structural determination. 1 exhibits a 3D anionic structure with the binodal 4,8-connected network
with Schläfli symbol {46}2{49·618·8}, consisting of Cu6 clusters
and L1 ligands. In contrast, complex 2 possesses a different
3D network with trinodal 3,4,6-c topology with Schläfli symbol
{4·62}2{42·66·85·102}­{64·8·10}.
In these two complexes, the semirigid hexacarboxylate ligands adopt
distinct conformations to connect metal ions/clusters, which must
be ascribed to the addition of the auxiliary rigid ligand in reaction
systems. In addition, gas absorption properties of 1 and 2 including CO2 and N2 were further
investigated.