Metal　organic　frameworks　(MOFs)　are　a　class　of　porous　crystalline　materials　that　feature　a　series　of　unique　properties,　such　as　large　surface　area　and　porosity,　high　content　of　transition　metals,　and　possibility　to　be　designed　and　modified　after　synthesis,　that　make　these　solids　especially　suitable　as　heterogeneous　catalysts.　The　active　sites　can　be　coordinatively　unsaturated　metal　ions,　substituents　at　the　organic　linkers　or　guest　species　located　inside　the　pores.　The　defects　on　the　structure　also　create　these　open　sites.　The　present　review　summarizes　the　current　state　of　the　art　in　the　use　of　MOFs　as　solid　catalysts　according　to　the　type　of　site,　making　special　emphasis　on　the　more　recent　strategies　to　increase　the　population　of　these　active　sites　and　tuning　their　activity,　either　by　adapting　the　synthesis　conditions　or　by　post-synthetic　modification.　This　review　highlights　those　reports　illustrating　the　synergy　derived　from　the　presence　of　more　than　one　of　these　types　of　sites,　leading　to　activation　of　a　substrate　by　more　than　one　site　or　to　the　simultaneous　activation　of　different　substrates　by　complementary　sites.　This　synergy　is　frequently　the　main　reason　for　the　higher　catalytic　activity　of　MOFs　compared　to　homogeneous　catalysts　or　other　alternative　solid　materials.　Besides　dark　reactions,　this　review　also　summarizes　the　use　of　MOFs　as　photocatalysts　emphasizing　the　uniqueness　of　these　materials　regarding　adaptation　of　the　linkers　as　light　absorbers　and　metal　exchange　at　the　nodes　to　enhance　photoinduced　electron　transfer,　in　comparison　with　conventional　inorganic　photocatalysts.　This　versatility　and　flexibility　that　is　offered　by　MOFs　to　optimize　their　visible　light　photocatalytic　activity　explains　the　current　interest　in　exploiting　these　materials　for　novel　photocatalytic　reactions,　including　hydrogen　evolution　and　photocatalytic　CO2　reduction.