Block from U+1F200 to U+1F2FF. This block was introduced in Unicode version 5.2 (2009). It contains 57 codepoints.
The Wikipedia provides the following information on block Enclosed Ideographic Supplement:
Enclosed Ideographic Supplement is a Unicode block containing characters for compatibility with the Japanese ARIB STD-B24 standard. It contains a squared kana word, and many CJK ideographs enclosed with squares, brackets, or circles.