Large Titanium-Oxo Clusters as Precursors to Synthesize the Single Crystals of Ti-MOFs

Titanium­(IV)-based metal-organic frameworks (Ti-MOFs) have received significant attention in recent years because of their numerous photocatalytic applications; however, the synthesis of new Ti-MOFs with precise crystal structures is still challenging. Herein, three new Ti-MOFs with single-crystal structures (denoted as FIR-125–FIR-127) are rationally synthesized by employing a large Ti44-oxo cluster as the precursor to assembly with the organic ligand. Big single-crystals can be successfully obtained and structurally determined by single-crystal X-ray diffraction. During the synthesis, the large Ti44-oxo cluster is transferred to small Ti8O8(CO2)16 building units in the Ti-MOF. In addition, FIR-125 exhibit high stability, permanent porosity, and photocatalytic activity. This work provides a new strategy toward the big crystal growth of Ti-MOFs through the slow transformation of large titanium-oxo clusters.

近年来，钛(IV)基金属有机框架（Titanium(IV)-based metal-organic frameworks，缩写Ti-MOFs）凭借其在光催化领域的多样应用受到广泛关注；然而，合成具备精确晶体结构的新型Ti-MOFs仍颇具挑战。本研究以大型Ti₄₄氧簇作为前驱体，与有机配体组装，理性合成了三种具有单晶结构的新型Ti-MOFs（命名为FIR-125至FIR-127）。研究成功获得了大尺寸单晶，并通过单晶X射线衍射完成了结构解析。合成过程中，大型Ti₄₄氧簇会转化为Ti-MOFs中的小型Ti₈O₈(CO₂)₁₆结构基元。此外，FIR-125展现出优异的稳定性、永久孔隙率与光催化活性。本工作通过大型钛氧簇的缓慢转化，为Ti-MOFs的大尺寸单晶生长提供了全新策略。