Two porous nets have been prepared via a 2-step crystal engineering approach that links decorated trigonal prismatic [Cr3([small mu ]3-O)(CO2)6] and [Cu3([small mu ]3-Cl)(RNH2)6Cl6] molecular building blocks, MBBs. tp-PMBB-5-acs-1 is a rare example of a rigid acs underlying net whereas tp-PMBB-6-stp-1, an stp underlying net, exhibits free NH2 groups in its channels and a relatively high isosteric heat of adsorption for CO2.