MnNb2O6 nanosheets (P-MNOs) is selectively crystallized by using surface capping ligand with functional sulfonate group (sodium dodecyl benzene sulphonate), which binds to the (131) surface of MnNb2O6 inducing the morphology-controlled crystallization of MnNb2O6 materials. Surface modification of photoactive P-MNOs with electron-rich oxalic acid ligands establishes an excited surface complex layer on phase-pure P-MNO as evidenced by spectroscopic analyses (FT-IR, UV vis, Raman, PL, etc.), and thus more efficiently photocatalyzes the reduction of Cr(VI) into Cr(III) than solely P-MNOs or oxalic acid under visible light (lambda >420 nm) via a ligand-to-metal interfacial electron transfer pathway. However, the interaction between oxalic acid and MnNb2O6 is highly dependent upon the morphology of solid MnNb2O6 substrate due to the higher surface-area-to-volume ratio and higher surface activity of (131) planes in the sheet-like morphology. This study could assist the construction of stable niobate material systems to allow a versatile solid surface activation for establishing more energy efficient and robust catalysis process under visible light. (C) 2017 Elsevier B.V. All rights reserved.