Harvesting energy gases in the nanoporous water-frameworks of clathrate hydrate enables the widespread of hydrogen-based fuels converted from excess solar or wind energy sources (i.e., Power-to-Gas). However, there has always been a critical trade-off between mild formation condition and maximum working capacity. Here we demonstrate the ‘natural gas modulator’ based synthesis that leads to significantly reduced synthesis pressure ( P H 2 ≈3 MPa) simultaneously with the formation of hydrogen clusters (up to 3 molecules) in the confined nanoporous cages of clathrate hydrates. Instead of employing hazardous liquid chemicals, clean energy gas of natural gas is used for the first time to multiply load H 2 in all cages (512, 51262, and 51264 cages) of hydrogen-natural gas hydrates without any postsynthetic modification (e.g., guest-exchange reaction). This approach minimizes the environmental impact and reduces operation cost since clathrate hydrates do not generate any chemical waste in both synthesis and decomposition process, and hydrogen-natural gas mixture can be also utilized as an energy resource as itself.