Monolayer　H1.4Ti1.65O4　center　dot　H2O　nanosheet　(denoted　as　NST)　has　been　prepared　as　a　photocatalyst　for　the　oxidation　of　furfuryl　alcohol　(denoted　as　FA)　to　furaldehyde　under　visible　light　irradiation.　The　photocatalytic　activity　of　NST　is　over　10　times　higher　than　that　of　its　layered　counterpart.　This　enhanced　activity　may　be　attributed　to　the　high　percentage　of　exposed　Lewis　acid　sites　in　NST.　The　in-situ　FTIR　result　suggests　that　FA　are　efficiently　chemosorbed　on　the　exposed　Lewis　acid　sites　forming　the　surface　coordination　species　via　C-O　groups,　resulting　in　the　activation　of　FA.　The　surface　coordination　species　would　respond　to　visible　light　absorption.　Furthermore,　The　XAFS　result　shows　that　the　signals　for　Ti-O　and　Ti-Ti　in　NST　are　weaker　dramatically　and　the　signals　positions　are　shifted　by　0.03　angstrom　in　the　higher　R　direction　as　compared　with　those　in　layered　counterpart,　suggesting　the　more　exposed　Ti　and　0　defects　in　NST.　The　oxygen　molecules　absorbed　on　these　surface　defects　are　activated　forming　center　dot　O-2(-)　by　photo-electrons　under　visible　light　irradiation.　Finally,　a　possible　mechanism　has　been　proposed　at　a　molecular　level.