Abstract:
Two-dimensional metal-organic frameworks (2D-MOFs) are low-dimensional hybrid
organic-inorganic materials synthesized via coordinating planar multidentate ligands
with metal nodes to form an extended coordination network. Such 2D-MOFs are
emerging as next-generation 2D crystalline solids for energy-based applications.
Similar to their 3D counterparts, 2D-MOFs exhibit high crystallinity and porosity, along
with superior orbital overlap, which engenders them with efficient charge storage and
facile charge transfer. However, for practical applications, the performance needs to be
improved; therefore, combining 2D-MOF with various 2D matrices via chemical
interaction is expected to enhance the overall electrical and/or electrochemical
properties. Herein, we demonstrate an unconventional strategy to integrate a 2D-MOF,
namely Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with
functionalized graphene, i.e., reduced graphene oxide (rGO) by an in-situ reductionoxidation
reaction. We have also carried out an in-depth comparative study with
traditional methods. The composite, namely Cu-HHTP/rGO, was studied using
techniques like Electron Spin Resonance (ESR), Raman, and X-ray Photoelectron
Spectroscopy (XPS) for probing the possible chemical interaction. Cu-HHTP/rGO
demonstrates a markedly high increment in electrical conductivity, along with a fourfold
enhancement in BET surface area compared to pristine Cu-HHTP. The Seebeck
coefficient suggests the change in semiconducting behavior from n-type in Cu3(HHTP)2
to p-type in Cu-HHTP/rGO, along with a high thermoelectric power factor. The Cu-
HHTP/rGO composite was studied for supercapacitor application. The capacitance
values were enhanced by almost two-fold in both solid and liquid state configurations,
compared to pristine Cu-HHTP. We anticipate that the unconventional chemical
approach proposed in this work can be used to combine various 2D-MOFs with different
2D matrices, which can then be explored for wide-scale applications.
