Despite　numerous　inherent　merits　of　metal-organic　frameworks　(MOFs),　structural　fragility　has　imposed　great　restrictions　on　their　wider　involvement　in　many　applications,　such　as　in　catalysis.　Herein,　a　strategy　for　enhancing　stability　and　enabling　functionality　in　a　labile　Zr(IV)-MOF　has　been　proposed　by　in　situ　porphyrin　substitution.　A　size-　and　geometry-matched　robust　linear　porphyrin　ligand　4,4　＇-(porphyrin-5,15-diyl)dibenzolate　(DCPP2-)　is　selected　to　replace　the　4,4　＇-(1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-2,7(1H,3H,6H,8H)-diyl)dibenzoate　(NDIDB2-)　ligand　in　the　synthesis　of　BUT-109(Zr),　affording　BUT-110　with　varied　porphyrin　contents.　Compared　to　BUT-109(Zr),　the　chemical　stability　of　BUT-110　series　is　greatly　improved.　Metalloporphyrin　incorporation　endows　BUT-110　MOFs　with　high　catalytic　activity　in　the　photoreduction　of　CO2,　in　the　absence　of　photosensitizers.　By　tuning　the　metal　species　and　porphyrin　contents　in　BUT-110,　the　resulting　BUT-110-50%-Co　is　demonstrated　to　be　a　good　photocatalyst　for　selective　CO2-to-CO　reduction,　via　balancing　the　chemical　stability,　photocatalytic　efficiency,　and　synthetic　cost.　This　work　highlights　the　advantages　of　in　situ　ligand　substitution　for　MOF　modification,　by　which　uniform　distribution　and　high　content　of　the　incoming　ligand　are　accessible　in　the　resulting　MOFs.　More　importantly,　it　provides　a　promising　approach　to　convert　unstable　MOFs,　which　mainly　constitute　the　vast　MOF　database　but　have　always　been　neglected,　into　robust　functional　materials.