Synthesis and characterization of (Co1-x Nix)3(BTC)2.12H2O (0 ≤ x ≤ 0.5) MOF based Janus chemical micromotors

Abstract

We report the synthesis and characterization of Metal–Organic Framework (MOF)-Based Janus chemical Micro motors that self-propel at 26 and 25 µms−1 in 5% and 12% of H2O2, respectively, via ionic diffusiophoresis. The synthesis of this MOF was achieved by solvothermal method. The TG -DT analysis study on (Co1-x Nix)3(BTC)2·12H2O (0 ≤ x ≤ 0.5) micro motors, showed that water ligands can be easily removed. The Co3(BTC)2·12H2O crystallized in orthorhombic crystal system with Pmmm space group and (Co0.8Ni0.2)3(BTC)2·12H2O, (Co1.5Ni1.5)3(BTC)2·12H2O crystallized in monoclinic crystal system with C2 space group. The lattice constants, dislocation density and micro strain of the micro motors were calculated and the structure is discussed in detail using crystal viewer. The morphology of (Co1-x Nix)3(BTC)2·12H2O (0 ≤ x ≤ 0.5) micro motors were scrutinized using the field emission scanning electron microscopy (FE-SEM). Energy dispersion X-ray (EDX) analysis was employed for the elemental analysis and chemical characterization. The vibrational characterization was studied by utilizing Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectroscopy. The asymmetric and symmetric stretching vibrations of 1,3,5 trisubstituted aromatic ring appeared as three bands at 1368, 1428 and 1219 cm−1. The optical properties were explored using UV–Visible DRS and the absorption edge of Co-BTC, Co0.8Ni0.2-BTC and Co0.5Ni0.5-BTC were observed at approximately 300 nm, 450 nm and 500 nm respectively. The direct band gap for (Co1-x Nix)3(BTC)2.12 H2O (0 ≤ x ≤ 0.5) micromotors was found to be 3.84 eV, 3.76 eV and 3.66 eV respectively. The pore-size distribution and specific surface areas were calculated using Barrett–Joyner–Halenda, BJH and Brunauer Emmett-Teller method respectively. The average pore diameter 8.727 nm and total pore volume of 2.467 × 10−2cm3g−1 was obtained for the material. Insertion of nickel in the lattice of cobalt further accelerates the speed from 0.08 µms−1 to 26µms−1, which leads to a force of 7.29 fN and a power of 4.9 × 10−9 fW, which resembles bio molecular motors. Considering the investigation of MOFS as Microbots/Micromotors so far, Co0.8Ni0.2BTC in both 5% and 12% H2O2 can be represented as the best example of clear observation of bubble tails propelling spherical Janus micromotors.