Lawrence Berkeley National Laboratory

Efficient removal of heterocyclic organosulfur compounds from fuels can relieve increasingly serious environmental problems (e.g., gas exhaust contaminants triggering the formation of acid rain that can damage fragile ecological systems). Toward this end, novel metal-organic frameworks (MOFs)-based sorbent materials are designed and synthesized with distinct hard and soft metal building units, specifically {[Yb₆Cu₁₂(OH)₄(PyC)₁₂(H₂O)₃₆]·(NO₃)₁₄·xS} _n (QUST-81) and {[Yb₄O(H₂O)₄Cu₈(OH)_8/3(PyC)₈(HCOO)₄]·(NO₃)_10/3·xS} _n (QUST-82), where H₂PyC = 4-Pyrazolecarboxylic acid. Exploiting the hard/soft duality, it is shown that the more stable QUST-82 can preserve desulfurization efficiency in the presence of competing nitrogen-containing contaminate. In addition, thermodynamically controlled single-crystal-to-single-crystal (SC-SC) phase transition is uncovered from QUST-81 to QUST-82, and in turn, mechanistic features are probed via X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, and ab initio molecular dynamics simulations.