Clay-based　2D　nanofluidics　are　promising　candidates　for　promoting　practical　application　of　osmotic　energy　harvesting　owing　to　their　low　cost　and　simple　large-scale　preparation,　but　they　usually　suffer　from　poor　mechanical　strength　and　unsatisfactory　ion　selectivity.　Herein,　the　nanofiber　reinforcement　strategy　is　proposed　to　address　these　two　key　issues　of　clay-based　2D　nanofluidics　for　achieving　highly-efficient　osmotic　energy　harvesting.　The　aramid　nanofibers　(ANFs)　are　intercalated　into　lameller　montmorillonite　(MMT)　membrane　to　construct　robust　2D　nanofluidics.　In　this　configuration,　the　introduction　of　negatively-charged　ANFs　greatly　enhances　the　mechanical　strength　of　MMT　nanofluidic　membrane,　and　further　improves　the　cation　selectivity　towards　high-efficient　osmotic　energy　conversion.　The　ANF-reinforced　MMT　nanofluidics　could　delivery　a　maximum　power　output　up　to　~5.16　W　m−2　under　50-fold　salinity　gradient　(KCl)　simulating　sea/river　junction　environment,　which　is　remarkably　superior　to　almost　all　reported　clay-based　2D　nanofluidics.　The　osmotic　power　can　be　further　increased　to　6.45　W　m−2　at　a　higher　temperature　of　50　ºC.　Furthermore,　the　2D　nanofluidic　membrane　can　withstand　extreme　water　environments　such　as　strong　acidity/alkalinity　and　high　salinity　for　over　20　days.　This　work　is　envisaged　to　provide　a　new　strategy　in　the　construction　of　robust　clay-based　2D　nanofluidics　towards　pushing　osmotic　energy　harvesting　into　real-world　applications.　©　2022　Elsevier　Ltd