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 ( μ 3 - O ) 6 ( μ 2 - OH ) 6 ] n secondary building units (SBUs) and tritopic carboxylate linkers 4,4',4″-nitrilotribenzoic acid (H₃TCA), 1,3,5-tris(4-carboxyphenyl) benzene (H₃BTB) and tris(4'-carboxybiphenyl)amine (H₃BTCA), 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 H₂ production rate of ZSTU-1 and ZSTU-3 being 3-4 times higher than that of ZSTU-2. The photocatalytic H₂ production rates for ZSTU-1, ZSTU-2, and ZSTU-3 are 1060 μmol g^-1 h^-1, 350 μmol g^-1 h^-1 and 1350 μmol 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.