Two new isostructural porous supramolecular materials {[Cu2(amp)4Cl][M(C2O4)3]·6H2O}n (amp = 2-aminomethylpyridine), designated as II and III for M = Cr(III) and M = Fe(III) respectively, have been synthesized by a self-assembly process of two ionic complexes [Cu2(amp)4Cl]3+ and [M(C2O4)3]3–, M = Fe(III) and Cr(III). They build heterometallic hydrogen-bonded-, oxalato- and chlorido-bridged zigzag chains with interchain hydrogen bonds and π–π interactions. This results in supramolecular potentially porous architectures exhibiting large channels filled with hexameric water clusters. Their activated phases, II′ and III′, can readsorb the water molecules to regenerate the initial materials which are stable for many water adsorption and desorption cycles like that of their homologous catena-{[(Co(amp)3][Cr(C2O4)3]·6H2O} (I′). The three materials I′, II′, and III′ exhibit water adsorption and desorption isotherms having a sigmoidal shape and resulting in the combination of a type I(b) profile followed by an S-s...