Ionic solid

An ionic solid, comprising:

• a metal complex comprising (A) an anionic metal complex and (B) a cationic species, arranged through a coordination bond or an ionic bond into a crystal lattice;
• pores, suitable for incorporating a guest compound, formed by the crystal lattice;
• and
• a hydrophilic substance having a molecular weight of 60 or larger comprised in the pores as the guest compound,
• wherein the hydrophilic substance is at least one selected from the group consisting of a polyhydric alcohol, a cyclic oligosaccharide, a saccharide, and a sugar alcohol,
• wherein the anionic metal complex (A) has formula (1):
• [(M1)d(M2)e(X1)f]k− (1),
• M1 independently being a group 9 metal element, M2 independently being a group 11 metal element, X1 being an amino acid having a thiol group, d and 3 independently being a number in a range of from 0 to 4, provided d and e are not simultaneously 0, f being a number in a range of from 1 to 8, and k being a number in a range of from 1 to 4, and
• wherein the cationic species (B) has formula (2):
• Aa[(M3)l(X2)m]j (2),
• A being an alkali metal ion or an alkaline earth metal ion, M3 being a group 9 or 12 metal element, each X2 independently being water, ammine, diamine, a nitrite ion, and/or carboxylate, a being a number in a range of from 0 to 10, l being a number in a range of from 0 to 1, provided that a and l are not simultaneously 0, m being a number in a range of from 1 to 6, and j being a number in a range of from 1 to 3.