Thermal Exfoliation of Layered Metal–Organic Frameworks into Ultrahydrophilic Graphene Stacks and Their Applications in Li–S Batteries

2D nanocarbon-based materials with controllable pore structures and hydrophilic surface show great potential in electrochemical energy storage systems including lithium sulfur (Li–S) batteries. This paper reports a thermal exfoliation of metal–organic framework crystals with intrinsic 2D structure into multilayer graphene stacks. This family of nanocarbon stacks is composed of well-preserved 2D sheets with highly accessible interlayer macropores, narrowly distributed 7 Å micropores, and ever most polar pore walls. The surface polarity is quantified both by its ultrahigh water vapor uptake of 14.3 mmol g⁻¹ at low relative pressure of P/P ₀ = 0.4 and ultrafast water wetting capability in less than 10.0 s. Based on the structural merits, this series hydrophilic multilayer graphene stack is showcased as suitable model cathode host for unveiling the challenging surface chemistry issue in Li–S batteries.

A hydrophilic porous graphene stack is fabricated through a facile thermal transformation of the metal–organic framework crystals with intrinsic 2D structures. The polar surface favors confinement of polysulfide intermediates in a highly electron and ion accessible pores, and thus the coupled redox reaction proceeds in a highly reversible manner in an operating Li–S battery.

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