0D/2D heterojunctions,e specially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility.H erein, unprecedent heterojunctions of vanadate (AgVO 3 ,B iVO 4 ,I nVO 4 and CuV 2 O 6 )Q Ds/graphitic carbon nitride (g-C 3 N 4 )N Ss exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up-conversion absorption, and nitrogen coordinating sites of g-C 3 N 4 NSs,h ighly dispersed vanadate nanocrystals,aswell as the strong coupling and band alignment between them lead to superior visible-light-driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts.T his work is expected to provide anew concept to construct multifunctional 0D/2D nanocomposites for al arge variety of opto-electronic applications,n ot limited in photocatalysis.For decades,0-dimensional (0D) semiconductive QDs have attracted great attention due to their unique advantages of small size (< 10 nm), large surface area, short effective charge-transfer length and size-tunable optoelectronics, [1] which make them highly promising in using the photoexcited charges in the field of photodetectors,p hototransistors, photovoltaic devices,a nd photocatalysts.[2] However,s everal drawbacks largely restrict their practical applications. [1a,2b, 3] First, QDs are vulnerable to self-aggregation;a bundant surface defects make them unstable in comparison with their bulk counterparts;m oreover,t he high photoluminescence of QDs results in heavy recombination of photoexcited charges.[4] One of the most efficient routes to solve these problems is to load QDs onto ultrathin 2-dimensional (2D) NSs (e.g. graphene) to form a0 D/2D nanocomposite. [5] Interactions between two moieties can make QDs more dispersive and stable,w hile the accelerated charge transfer facilitated by 2D NSs can effectively quench the photoluminescence of QDs,thereby suppressing the recombination of photoexcited charges.T hus,s ubstantially enhanced optoelectronic performance is achieved by the 0D/2D composites in efficient utilization of photoexcited charges. [5] Recently,0 D/2D composite photocatalysts/photoelectrodes have been greatly developed, in which the coupling of QDs and graphene NSs is the most successful illustration. Due to the large surface area and high electrical conductivity of graphene,t he loaded semiconductive QDs (nanocrystals) are endowed with superior charge transfer and separation capability,t hereby presenting greatly promoted photocatalytic activity or/and photocurrent.[6] Forexample,Y uand coworkers [6a] loaded TiO 2 nanocrystals (< 10 nm) on graphene NSs,which displayed the best apparent quantum efficiency of 9.7 %a t3 65 nm;F ang et al.[6b] and Liu and co-workers [6c] respectively incorporated CdS QDs onto graphene NSs, bringing enhanced photocatalytic and PEC performance. However,t he largely consumed graphene NSs (volume ratio even higher than 50...