Functionalization of metal–organic frameworks with cuprous sites using vapor-induced selective reduction: efficient adsorbents for deep desulfurization†
Functionalization of metal–organic frameworks (MOFs) with Cu(I) sites is extremely desirable for various applications including adsorption, catalysis, and sensing. The traditional method for the conversion of supported Cu(II) to Cu(I) is high-temperature autoreduction (HTA), which produces Cu(I) with an unsatisfactory yield (ca. 50%) but requires quite harsh conditions (e.g. 700 °C, 12 h) that are unsuitable for MOFs. Here we report the rational design of an efficient, controllable strategy for the conversion of supported Cu(II) to Cu(I) by using vapor-induced selective reduction (VISR), in which vapors of weak reducing agents (e.g. methanol) diffuse into the pores of MOFs and interact with Cu(II) precursors. This strategy allows the fabrication of Cu(I) sites with a 100% yield without the formation of Cu(0) at much lower temperatures (e.g. 200 °C, 6 h) and subsequently preserves the structure of MOFs well. Due to the abundant Cu(I) sites and high porosity of MOF supports, the obtained materials exhibit excellent performance in adsorptive desulfurization with regard to capacity, selectivity, and recyclability.