SrU3(SeO7)2(O2)2 crystallizes in the monoclinic C2 space group. The structure consists of four hydrogen peroxide molecules inside a SrU3(SeO7)2 framework. In the SrU3(SeO7)2 framework, Sr(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted SrO6 pentagonal pyramids that share corners with four equivalent U(1)O7 pentagonal bipyramids. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent Sr(1)O6 pentagonal pyramids and  an edgeedge with one U(1)O7 pentagonal bipyramid. In the second U site, U(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms. Se(1) is bonded in a trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1) and one U(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Sr(1) and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sr(1) and one U(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Se(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Se(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one U(1) and one Se(1) atom.
SrU3(SeO7)2(O2)2 crystallizes in the monoclinic C2 space group. The structure consists of four hydrogen peroxide molecules inside a SrU3(SeO7)2 framework. In the SrU3(SeO7)2 framework, Sr(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted SrO6 pentagonal pyramids that share corners with four equivalent U(1)O7 pentagonal bipyramids. Both Sr(1)-O(3) bond lengths are 2.76 Å. Both Sr(1)-O(4) bond lengths are 2.66 Å. Both Sr(1)-O(5) bond lengths are 2.61 Å. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent Sr(1)O6 pentagonal pyramids and  an edgeedge with one U(1)O7 pentagonal bipyramid. The U(1)-O(1) bond length is 2.24 Å. The U(1)-O(2) bond length is 2.26 Å. The U(1)-O(4) bond length is 1.86 Å. The U(1)-O(5) bond length is 1.86 Å. The U(1)-O(6) bond length is 2.38 Å. The U(1)-O(7) bond length is 2.39 Å. The U(1)-O(8) bond length is 2.37 Å. In the second U site, U(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms. The U(2)-O(1) bond length is 2.25 Å. The U(2)-O(2) bond length is 2.26 Å. Both U(2)-O(3) bond lengths are 1.84 Å. Both U(2)-O(6) bond lengths are 2.64 Å. Both U(2)-O(7) bond lengths are 2.61 Å. Se(1) is bonded in a trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. The Se(1)-O(6) bond length is 1.73 Å. The Se(1)-O(7) bond length is 1.74 Å. The Se(1)-O(8) bond length is 1.71 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1) and one U(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Sr(1) and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sr(1) and one U(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Se(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Se(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one U(1) and one Se(1) atom.