  Two-dimensional boron structures, due to the diversity of properties, attract
great attention because of their potential applications in nanoelectronic
devices. A series of \ce{TiB_x} ($4\leq x \leq 11$) monolayers are efficiently
constructed through our motif based method and theoretically investigated
through high-throughput first-principles calculations. The configurations are
generated based on motifs of boron triangular/quadrilateral fragments and
multicoordinate titanium-centered boron molecular wheels. Besides priviously
reported \ce{TiB4} which was discovered by global search method, we predict
that high symmetry monolayers \ce{TiB7} (Cmmm) and \ce{TiB9} (P31m) which are
octa-coordinate and nona-coordinate titanium boride are thermodynamic stable.
The \ce{TiB7} monolayer is a BCS superconductor with the transition temperature
$T_c$ up to 8K. The motif based approach is proved to be efficient in searching
stable structures with a prior knowledge so that the potentially stable
transition metal monolayers can be quickly constructed by using basic cluster
motifs. As an efficient way of discovering materials, the method is easily
extended to predict other type of materials which have common characteristic
pattern in the structure.
