Rational Formation of Porous Pillared Alloxazine-Based Metal–Organic Frameworks: Pore-Opening Effect and Redox Properties

A modular one-pot three-component and mixed ligand strategy was used to synthesize metal–organic frameworks (MOFs) by combining Co and Zn metal salts with 2,6-naphthalenedicarboxylic acid (H2ndc) and a redox-active alloxazine-based ligand (1 or 2) under solvothermal conditions. Structural elucidation by X-ray diffraction highlights the pivotal role of linker topology in directing framework dimensionality. Indeed, substitution of ligand 1 by its positional isomer, 1,4-di(pyridin-3-yl)benzene (ligand 2), under identical synthetic conditions yields a dense, non-porous coordination compound with the same M/ndc stoichiometry. The Zn-based framework (1–Zn) displays structural robustness and multifunctional behavior. High-pressure gas sorption measurements reveal a pressure-induced gradual pore-like-opening response toward CO2 and C2H4 adsorption up to 20 bar, in agreement with variable-pressure powder X-ray diffraction (VP-PXRD) analyses. Electrochemical investigations further evidence reversible, ligand-centered redox activity, enabling the integration of 1–Zn as an active electrode material in a Li-ion device, where galvanostatic cycling reveals, for the first time, reversible Li+ insertion in MOF-bearing alloxazine motifs. These findings establish the first example of a pillared MOF incorporating an alloxazine-derived linker and underscore the potential of redox-active MOFs as tunable materials for gas separation and electrochemical energy storage.