Metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and related molecular porous materials have entered a stage where not just the porosity, but other physical attributes are now playing a major role in their properties. Catalytic properties rivalling those of classic heterogeneous catalysts are being unearthed. Photophysical properties enabled by both the rigidity and the controlled dynamics of the porous environment are making strides from both fundamental and applied perspectives. Applications in energy storage are emerging, enabled by important advances in increasing the electrical and ionic conductivity in these materials. Exciting magnetic properties are being reported in such materials with increasing frequency as well, suggesting that perhaps porous magnets and possibly superconductors are also within reach. This Faraday Discussion explores several important new directions in the chemistry of porous crystalline materials. It develops a fundamental understanding of key aspects in the chemistry of porous crystalline materials: chemical properties, electronic properties and physical properties.