By modulating the secondary building units derived from the primary building units, N-acylsalicylhydrazides (H-3-xshz), we have been able to construct isostructural but tunable host networks, [Mn-6(xshZ)(6)(dmf)(2)(bpea)(2)], with different cavity sizes and shapes where the secondary building units, [Mn-6(xshz)(6)], were linked through exo-bidentate bridging ligand, 1,2-bis(pyridyl)ethane (bpea) to form 3-D networks. With a short length linear N-acyl side chain at the primary building unit, the host networks have a 3-D network with three-dimensional cavities. With an appropriate length linear N-acyl side chain at the primary building unit, the host network keeps the isostructural 3-D network but with two types of one-dimensional channels of reduced cavity volume. The tuned host networks showed not only size selectivity for the guest molecules but also shape selectivity. While the three-dimensional channeled host showed selectivity depending on the length of the podal guests, the one-dimensional channeled host showed selectivity depending on both the length and/or the podality of the guest molecules.