New water-soluble 1D and 3D Cu-II/Na coordination polymers 1-3 bearing unprecedented [Cu-4(Hbes)(4)] cores have been easily generated by aqueous-medium self-assembly and fully characterized, thus opening up the use of the common biological buffer H(3)bes, (HO3SCH2CH2)N(CH2CH2OH)(2), in synthetic coordination chemistry. Apart from representing the first isolated and structurally characterized coordination compounds derived from H(3)bes, 1-3 show a remarkable promoting effect in the mild aqueous-medium hydrocarboxylation, by CO and H2O, of gaseous alkanes (C3H8 and n-C4H10) to the corresponding carboxylic acids, which are obtained in up to 95% yields based on the alkane.