Tunable titanium metal-organic frameworks with infinite 1D Ti-O rods for efficient visible-light-driven photocatalytic H2 evolution

Infinite 1D Ti-O rod-based metal-organic frameworks (MOFs) are promising photocatalysts for water splitting due to their high optical response and favourable photo-redox properties and stability, but have not been explored yet. In this study, three isoreticular porous 1D rod-based Ti-MOFs ZSTU-1, ZSTU-2 and ZSTU-3 are successfully constructed from infinite [Ti-6((3)-O)(6)((2)-OH)(6)](n) secondary building units (SBUs) and tritopic carboxylate linkers 4,4,4-nitrilotribenzoic acid (H(3)TCA), 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB) and tris(4-carboxybiphenyl)amine (H(3)BTCA), respectively. Their porosities systematically increase with the larger and longer organic linkers. The two MOFs ZSTU-1 and ZSTU-3 built from the triphenylamino-based ligands can absorb visible light, exhibiting much better photocatalytic performance than ZSTU-2 as shown by the H-2 production rate of ZSTU-1 and ZSTU-3 being 3-4 times higher than that of ZSTU-2. The photocatalytic H-2 production rates for ZSTU-1, ZSTU-2, and ZSTU-3 are 1060 mol g(-1) h(-1), 350 mol g(-1) h(-1) and 1350 mol g(-1) h(-1), respectively. The extraordinary photocatalytic activity of ZSTU-3 is attributed to its visible light absorption, large surface area, and favorable charge separation.