  We report the magnetic properties in the Co- and Zn-doped spin-1/2
honeycomb-lattice compound In$_3$Cu$_2$VO$_9$. The magnetic susceptibility and
specific heat experiments show no long-range ordering down to 2 K in
In$_3$Cu$_2$VO$_9$. In the low temperature range, approximately
T$^{2}$-dependent magnetic specific heat and linearly T-dependent spin
susceptibility were observed, suggesting a spin liquid candidate with a S = 1/2
honeycomb lattice. When Cu$^{2+}$ ions are partially substituted by Co$^{2+}$
ions, both impurity potential scattering and magnetic impurity scattering
induced by magnetic Co$^{2+}$ ions break the homogenous spin-singlet spin
liquid state, and lead to an antiferromagnetic(AFM) long-range correlation.
While replacing Cu$^{2+}$ with nonmagnetic Zn$^{2+}$ ions, the frustration and
antiferromagnetic correlation between Cu$^{2+}$ ions is weakened, leading to
breakage of a spin liquid state and suppression of the low-dimensional AFM.
