Modulator-Directed Counterintuitive Catenation Control for Crafting Highly Porous and Robust Metal-Organic Frameworks...

Sulfur dioxide (SO₂) is an important industrial feedstock that can be directly utilized or catalytically transformed to value-added chemicals such as sulfuric acid. The development of regenerable porous sorbents for the highly efficient storage and energy-minimal release of toxic SO₂ operating under ambient conditions has attracted growing interest. Herein, we report the topology-guided construction of highly porous acs-type metal-organic frameworks (MOFs) through a counterintuitive modulator-directed catenation control approach. In contrast to the conventional modulator facilitated coordination competition that favors the thermodynamic catenated phase, we show that the elevation of modulator concentration can promote the formation of the noncatenated phase probably through a sublattice dissolution pathway. The assembly of a custom-designed trigonal prismatic triptycene-quinoxaline linker and trinuclear Fe₃O cluster affords either the threefold catenated SJTU-219 or noncatenated SJTU-220 with desired acs net. Impressively, the synthetic approach is applicable to various metal ions, including Al³⁺, V³⁺, and even Ti⁴⁺. The noncatenated SJTU-220 exhibits an extraordinary SO₂ sorption capacity of 29.6 mmol g^-1 at 298 K and 1 bar, surpassing all reported solid sorbents. The uptake capacity can be further raised to 35.6 mmol g^-1 via the replacement of Fe³⁺ with kinetically more inert Cr³⁺, resulting in a staggering ∼329-fold volume reduction compared with free ideal SO₂ gas. Computational simulations suggest that unique Fe³⁺···S(SO₂) interactions dominate the SO₂ seeding process, facilitating the efficient packing of SO₂ molecules in the large channels. Besides, the exceptionally low uptake at the low pressure region implies global weak framework-SO₂ interactions, which offer great potential for practically implementing an "easy-on/easy-off" SO₂ delivery system.