Polyoxometalate-based open frameworks (POM-OFs) are extended architectures incorporating metal-oxide cluster units and comprise an emergent family of materials with a large diversity of topologies, structural flexibility and functionality at the nanoscale. Not only do POM-OFs present a wide range of configurable structures, but also a have a vast array of physical properties which reflect the properties of the various 'modular' molecular inputs. Here we describe the methodologies that can be used to construct POM-OF materials with important catalytic, electronic, and structural properties and discuss the advantages compared to the metal organic framework analogues. We also show that it is possible to construct POM-OF materials and design and/or fine tune their functionality by manipulating the initially generated building block libraries as well as by controlling the self-assembly towards the specific intermediate (POM) species which is the chemical and structural "information" carrier of the targeted POM-OF material.