Metal ion assistant transformation strategy to synthesize catechol-based metal-organic frameworks from Ti₃C₂T_x...

Chemical transformation strategy is capable of fabricating nanomaterials with well-defined structures and fascinating performance via controllable crystallization kinetics in the phase transformation. V₂CT_x MXene has been used as precursors to fabricate vanadium porphyrin metal-organic frameworks (V-PMOFs) via the coordination of deprotonated carboxylic acid ligands. However, the rational and in-depth exploration of synthesis mechanism with the aim of enriching the variety of MXene (i.e., Ti₃C₂T_x) and organic ligands (i.e., catechol-based) to design new MOFs is rarely reported. Herein, we have first developed a metal ion assistant transformation strategy to synthesize three-dimensional catechol-based TiCu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) MOFs with a non-interpenetrating SrSi₂ (srs) framework using two-dimensional Ti₃C₂T_x as precursors. The unique synergetic transformation mechanism involves the electron transfer from Ti₃C₂T_x to electrostatically adsorbed Cu²⁺ ion for redox reaction, the subsequent Ti-C bond rupture for Ti⁴⁺ ion release, and the continuous chelation coordination between Ti⁴⁺/Cu²⁺ and HHTP. Ti₃C₂T_x precursors and auxiliary metal ion could be rationally substituted by V₂CT_x and Mⁿ⁺ (e.g., Ni²⁺, Co²⁺, Mn²⁺, and Zn²⁺), respectively. This strategy lays the foundation for the design and synthesis of innovative and multifarious MOFs derived from MXene or other unconventional metal precursors.