The assembly of metal ions and organic linkers gives the highly regulated framework scaffolds, the so-called metal-organic framework (MOFs) or porous coordination polymers (PCPs). MOFs offer fascinating platforms in which light emitting components can be rationally incorporated. A variety of metal ions and organic linkers can be used to fabricate the MOF materials with a wide range of emissive properties. Besides their inherent luminescent properties, the permanent porosity of MOFs enables to accommodate guest species therein. The accommodation of guests in the pores results in the shift of emission wavelength, the change of emission intensity or even the generation of new emission bands. Therefore, the luminescent MOFs can be potentially exploited as a chemical sensor for small molecules or ions. In this chapter, we present a variety of luminescent properties derived from the guest accommodation in MOFs, and we discuss potential applications of luminescent MOFs as sensing materials.