The "edge-free" monolayer MoS2 films supported by 3D nanoporous gold show high catalytic activities towards hydrogen evolution reaction (HER), originating from large out-of-plane strains that are geometrically required to manage the 3D curvature of bicontinuous nano porosity. The large lattice bending leads to local semiconductor-to-metal transition of 2H MoS2 and the formation of catalytically active sites for HER.