This　review　describes　the　work　of　two　laboratories　in　the　field　of　the　modification　of　micro-　and　mesoporous　molecular　sieves　through　reactions　with　organometallic　complexes.　The　modification　of　zeolites　can　occur　inside　the　pore　channels　or　on　the　external　surface,　depending　on　the　size　of　the　organometallic　complex.　When　the　modification　occurs　on　the　external　surface,　it　results　in　a　decrease　of　the　pore　entrance,　which　will　lead　in　turn　to　a　modification　of　the　sorption　properties　of　the　zeolite,　by　decreasing　the　rate　of　the　adsorption　(mainly　by　a　kinetic　control).　Such　a　material　can　be　also　used　in　catalysis,　because　the　external　acid　sites,　which　are　responsible　for　side-reactions,　have　been　removed　upon　grafting.　When　small　organometallic　complexes　are　used,　they　can　fill　the　channels　and　cages　of　the　zeolite　and　react　with　internal　hydroxyl　groups.　Due　to　the　high　acidity　of　zeolites,　the　reaction　occurs　very　easily　(for　example　at　-100　°C　on　faujasite),　in　contrast　to　what　is　observed　on　the　external　surface,　therefore　leading　to　high　metal　loadings.　In　that　case,　the　modification　of　the　sorption　properties　will　be　mainly　related　to　a　thermodynamic　control.　The　resulting　materials　can　be　useful　in　catalysis,　by　combining　the　activity　of　the　organometallic　complex　and　properties　(for　example　shape-selectivity)　of　the　zeolite.　Modification　of　mesoporous　molecular　sieves　occurs　always　in　the　pores　and　results　in　altering　of　the　sorption　properties　of　the　solid,　by　changing　the　interaction　type　between　the　sorbent　and　the　sorbate.　For　example　the　sorption　isotherm　of　alkanes　is　changed　from　type　II　to　type　III　according　to　the　IUPAC　nomenclature.　©　2010　Science　China　Press　and　Springer-Verlag　Berlin　Heidelberg.