Hyper-crosslinked polymers (HCPs) have been produced by the Friedel-Crafts reaction using anthracene, benzene, carbazole or dibenzothiophene as precursors and dimethoxymethane as crosslinker, and the effect of graphene oxide (GO) addition has been studied. The resulting HCPs were highly microporous with BET areas (A BET) between 590 and 1120 m 2 g À1. The benzene-derived HCP (B1FeM2) and the corresponding composite with GO (B1FM2-GO) exhibited the highest A BET and were selected to study their hydrogen adsorption capacities in the pressure range of 0.1-14 MPa at 77 K. The maximum H 2 excess uptake was 2.1 and 2.0 wt% for B1FeM2 and B1FeM2-GO, respectively, at 4 MPa and 77 K. The addition of GO reduced the specific surface area but increased the density of the resultant HCP-GO composites, which is beneficial for practical applications and proves that materials giving higher gravimetric storage capacities are not necessarily those that offer higher volumetric capacities. H 2 adsorption-desorption cycles up to 14 MPa showed irreversible deformation of both HCP and HCP-GO materials, which calls into question their application for hydrogen adsorption at pressures above 4 MPa.