One approach to HCPs utilises non-functional aromatic compounds (i.e. without specifically polymerisable groups) that are 'knitted' together in a variety of ways, such as using external crosslinkers, 8 solvent stitching reactions, or Scholl reactions. Another approach produces HCPs via self-condensation reactions of chloromethyl or methyl ether moieties with aromatic carbon to form crosslinks. Hypercrosslinking requires only abundant Fe-or Al-based Lewis acid catalysts or simple organic acid catalysts. Owing to their low costs and broad design scope, HCPs are developed for a variety of applications including gas separation and storage, solid state extraction, and energy storage. HCPs also show promise in heterogeneous catalysis, both as inert frameworks or as active materials. HCP-based catalysts were employed for a wide array of transformations, ranging from biomass conversion to the photocatalytic reduction of CO2. High surface areas allow for an abundance of catalytically active sites and hierarchically porous structures are beneficial to the mass transfer of reactants and products. As such, HCPs show excellent ability in catalysis and are ideal candidates for industrial applications in accordance with the principles of green chemistry.