A three-phase copper MOF-graphene-polyaniline composite for effective sensing of ammonia

Highlights: • Composites of MOFs with graphene have been actively explored for the adsorption of small molecules. • The improved performance of such composites is demonstrated due to the synergistic effects. • Such effect has been imparted by the presence of defect sites (graphene) and high surface/volume ratio of MOFs. • Here, the potential of an MOF composite is explored as a conducting material for electrochemical sensing of NH_3. • This composite exhibited an extended detection range for NH₃ that is far better than the others tested previously. In this work, a three-phase composite material consisting of SiO₂-coated Cu-MOF, single layer graphene, and aniline was synthesized. In the presence of ammonium persulfate as an oxidant, the aniline component of this mixture was polymerized to polyaniline to bridge Cu-MOF and graphene in the composite. Hence, a new sensory material with a highly porous nature (MOF) and superior conduction properties (graphene/polyaniline) was constructed. More specifically, the inclusion of Cu-MOF in the matrix facilitated the acquisition of an electrochemically active sensory material with a high surface area of about 756 m²/g. The potential application of this porous semiconducting material was demonstrated for sensitive detection of ammonia in a linear detection range over 1–100 ppm with a low limit of detection of 0.6 ppm.