Fig. 5. View of (a) the crystal structure of MFM-512 showing hypothetical hydrogen bonding network with unbound water present in pores, a = 2.51 Å, b = 1.93 Å, c = 2.05 Å, d = 1.88 Å. (b) View of Ba(ii) node in MFM-511 showing restriction of the carboxyl proton a′ = 1.79 Å.