A boron-containing molecular sieve having the CHA crystal structure and comprising (1) silicon oxide and (2) boron oxide or a combination of boron oxide and aluminum oxide, iron oxide, titanium oxide, gallium oxide and mixtures thereof; and wherein the mole ratio of silicon oxide to boron oxide in said boron-containing molecular sieve is between 15 and 125. Also, a boron-containing molecular sieve, having a CHA crystal structure containing oxides only of (1) silicon and (2) boron; and wherein the mole ratio of silicon oxide to boron oxide in said boron-containing molecular sieve is between 15 and 125.