Core-shell metal-organic frameworks (MOFs) composed of MOFs as core (or shell) and another material, such as MOFs, carbon, inorganic compounds and organic polymers, as shell (or core), are a typical class of multifunctional MOFs composites. Because of the combination of the properties of core and shell materials, core-shell MOFs have better performances, such as increasing framework stability, selective separation and gas sorption, than the core or shell materials. Therefore, core-shell MOFs have high potentials for industrial applications. In this paper, the research progress of core-shell MOFs in recent years is reviewed. Synthesis methods and applications of variously structural core-shell MOFs, such as MOF@MOF, MOF@carbon, metal oxide@MOF, and polymer@MOF are introduced. Besides, the future development of core-shell MOFs is prospected.

Contents
1 Introduction
2 Synthesis methods and applications of variously structural core-shell MOFs
2.1 MOF@MOF
2.2 Core-shell structures of MOFs with carbon
2.3 Core-shell structures of MOFs with inorganic compounds
2.4 Core-shell structures of MOFs with organic polymers
3 Conclusion and outlook