The Catechism of the Catholic Church Defines Divorce
Divorce is a grave offense against the natural law. It claims to break the contract, to which the spouses freely consented, to live with each other until death. Sacramental marriage is the sign of the covenant of salvation, to which divorce does incredible injury. Contracting a new union, even if it is recognized by civil law, adds to the gravity of the rupture: the remarried spouse is then in a situation of public and permanent adultery. If a husband, separated from his wife, becomes involved with another woman, he is an adulterer because he makes that woman commit adultery; and the woman who lives with him is an adulteress, because she has drawn another's husband to herself.[2]
Furthermore, the Catechism states that divorce is immoral because “it introduces disorder into the family and into society. This disorder brings grave harm to the deserted spouse, to children traumatized by the separation of their parents and often torn between them, and because of its contagious effect which makes it truly a plague on society.â€[3]
But do we really believe that? Do we believe instead that the Church is “out of touch†with relationships and needs to “get with it?†The mentality of civil society challenges the divinely revealed truth that a valid marriage is an indissoluble union between a man and a woman. The Church responds by saying: “The Lord Jesus insisted on the original intention of the Creator who willed that marriage be indissoluble. He abrogates the accommodations that had slipped into the old Law. Between the baptized, ‘a ratified and consummated marriage cannot be dissolved by any human power or for any reason other than death.’â€[4]
I don't agree with this entirely...but withholding sex is not a valid reason for divorce in the Bible.