Optoelectronic Alteration of Metal-Organic Frameworks for Enhanced Photocatalytic Water Splitting Activity Under Solar Radiation

ABSTRACTMetal-organic frameworks (MOFs) have been increasingly popular in photocatalytic water-splitting research areas due to their unique, tunable porosity, high stability, large surface activity, and manipulative topology. However, the incapability of MOFs in harvesting broad-solar irradiation and rapid electron-hole pairs recombination has limited their efficiency in practical applications, and their structures allow researchers to manipulate them toward better efficiency. Also, linker modification is achieved by reclaiming the organic linker, which constructs MOFs by functionalizing, changing the ligand’s length, and using an aided organic linker. In addition, being a free space in their structure gives this opportunity to modify them easily with other compounds such as inorganic complex compounds and nanoparticles by incorporation, impregnation, and ship-in-a-bottle methods. The objectives of this review article are three-fold. First, to emphasize understanding of the fundamental correlation among promising strategies to improve the optoelectronic properties of MOFs such as light-harvesting capability and photoinduced electron-hole pairs for photocatalytic reactions involving water splitting reaction under broad solar irradiation. Second, to systematically summarize the organic linker modification and incorporation of polyoxometalate, coordination metal complexes, and various nanoparticles. Third, to discuss challenges and future research directions for the development of broad solar band activation of MOFs for photocatalysis purposes.Summary Investigation of the different methods for modification of MOFsReview of the incorporation of complex compounds into MOFs in detailInvestigation of all the strategies for incorporation of complex compounds into MOFsKEYWORDS: Photocatalystwater splittinglonger wavelengthmetal-organic compoundnanoparticle Abbreviation used PWS=Photocatalytic Water SplittingSTH=solar-to-hydrogenMOFs=Metal Organic FrameworksVB=Valence bandCB=Conduction bandHER=hydrogen evolution reactionNHE=Normal hydrogen electrodeOER=oxygen evolution reactionLMCT=ligand to metal charge transferLCCT=the linker‐to metal cluster charge transferPOM=polyoxometalateOMC=Organic-Metal CompoundsNPs=nanoparticlesEg=Energy band gapOMC@MOFs=Incorporation of organic-metal compounds with metal organic frameworksNPs@MOFs=Incorporation of nanoparticles with metal organic frameworksORR=oxygen reduction reactionMLCT=Metal ligand charge transferLSPR=localized surface plasmon resonanceHOCO=highest occupied crystal orbitalLUCO=lowest unoccupied crystal orbitalNB=None bondPCLEF=plasmonic concentrated local electromagnetic fieldCDs=Carbon nanodotsLLES=the low-lying excited statesMLCT=metal-to-ligand charge-transferLC=ligand-centeredMC=metal-centeredPL=photo-luminescentPEC=photoelectrochemicalCPs=Coordination polymersHOMO=Highest occupied molecular orbitalLUMO=Lowest unoccupied molecular orbitalHSAB=Hard and Soft Acids and BasesQDs=Quantum dotsODS=Oxidative desulfurizationRP=Reduction photocatalystOP=Oxidation photocatalystSBU=Secondary building unitEDTA=Ethylenediaminetetraacetic acidSHE=Standard hydrogen electrodeCLEF=concentrated local electromagnetic fieldAcknowledgmentsThis paper was supported by the Ferdowsi University of Mashhad Research Council and the RUDN University Strategic Academic Leadership Program.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe work was supported by the Ferdowsi University of Mashhad [3/56852]; RUDN University [AAAA-A19-119092390076-7].