Disclosed is a metal-organic framework composite including a host metal-organic framework, and nano metal-organic frameworks embedded in the host metal-organic framework. The host metal-organic framework and the nana metal-organic frameworks include different metals and organic ligands. The metal-organic framework composite has a structure in which the nano metal-organic frameworks are embedded in the host metal-organic framework. Due to this structure, defects are formed at the interfaces between the host metal-organic framework and the nano metal-organic frameworks, enabling the application of the metal-organic framework composite to gas storages with greatly improved gas storage efficiency. The metal-organic framework composite can be used as a gas adsorbent with very high efficiency due to its very large specific surface area. Also disclosed are a method for producing the metal-organic framework composite and a gas storage using the metal-organic framework composite.