We synthesised ten SHCPs from 4,4'-bis(chloromethyl)biphenyl using chlorosulfonic acid as a dual polymerisation catalyst and sulfonation agent (a general reaction scheme is shown in Figure ). Throughout the set, the ratio of chlorosulfonic acid to the aromatic monomer was varied to investigate the effect on the resulting SHCPs' textural and chemical properties. The progression from SHCP-1 to SHCP-10 follows an increasing catalyst-to-monomer ratio, precise values of which are given in Table . Briefly, 4,4'-bis(chloromethyl)biphenyl was dissolved in 1,2dichloroethane (1,2-DCE) and cooled using an ice bath, after which a solution of chlorosulfonic acid in 1,2-DCE was added to initiate polymerisation. Upon formation of a solid, the mixture was sealed and heated at 80 °C for up to 22 h. The resulting solid was then washed with methanol before drying to yield the SHCP. More details are given in the supporting information. It is worth noting that a shortened procedure in which the heating time was reduced to 3 h showed no apparent detriment to resulting SHCP properties. Polymers were typically produced in yields of >90 % when considering the incorporation of the acid catalyst as a sulfonic acid group. Networks ranged from a beige to dark brown colour with increasing catalyst to monomer ratios (Figure ).