Born at Stainforth in Yorkshire, Porter was educated at the universities of Leeds and Cambridge, where he obtained his PhD. After working on radar during World War II, he returned to Cambridge until, in 1955, he was appointed professor of chemistry at Sheffield University. From 1966 until 1985 he held one of the leading positions in British science, namely, the directorship of the Royal Institution and the Fullerian Professorship of Chemistry. In 1987 he was appointed professor (from 1990, chairman) of the Centre for Photomolecular Science at Imperial College, London.

In collaboration with his Cambridge teacher, Ronald Norrish, Porter developed from 1949 onward the new technique of flash photolysis. There were good reasons for thinking that the course of a chemical reaction was partly determined by a number of intermediate species too short-lived to be detected, let alone investigated. Porter therefore set out to study what he called the spectroscopy of transient substances.

The apparatus used involved a long glass or quartz tube containing the gas under investigation. This was subjected to a very brief pulse of intense light from flash tubes, causing photochemical reactions in the gas. The free radicals and excited molecules produced have only a transient existence, but could be detected by a second flash of light, directed along the axis of the reaction tube, used to record photographically an absorption spectrum of the reaction mixture. In this way the spectra of many free radicals could be detected.

In addition, it was possible to direct a continuous beam of light down the reaction tube and focus on one particular absorption line of a species known to be present. The change of this line with time allowed kinetic measurements of the rates of very fast gas reactions to be made.

The methods of flash photolysis have since been extended to liquids and solutions, to gas kinetics, and to the study of complex biological molecules such as hemoglobin and chlorophyll. Porter shared the Nobel Prize for chemistry in 1967 with Norrish and with Manfred Eigen for “their studies of extremely fast reactions effected by disturbing the equilibrium by means of very short pulses of energy.”

In 1990 Porter was raised to the British peerage as Baron Porter of Luddenham.