Kohn attended the Josefov Jewish School (then located in Břehová Street), and later on went to the Old Town high school at the Kinský Palace – Franz Kafka was a pupil here fifteen years later. Following on from his elder brother, Kohn began to study medicine at Prague University but left the course after just a few terms and changed his focus to music, studying with the famous concert maestro Mořic Wallerstein. Kohn then worked as an organist for many years, mainly in the Maisel Synagogue where he also served as choirmaster. He also played the organ in other synagogues and churches in Prague.

In August 1897, Kohn married Theresie Stein (1865-1936), a native of Nymburk . It was at this time that he witnessed the beginning of the reconstruction of the Prague ghetto, as well as the protests that were held by public figures from the world of Czech culture against the destruction of its cultural and historic sites. He may also have seen the famous master painters Jansa, Minařík and Slavíček with their pupils at work in the picturesque nooks of the ghetto. Josefov inhabitants were even more curious about the mysterious exploits of photographers such as Friedrich, Eckert and k íženecký, who, having meticulously adjusted their tripods and box cameras, would take shots of the ghetto while concealed under black cloaks. Another character Kohn would no doubt have bumped into was Zikmund Reach, the photographer and collector whose second-hand bookshop in Skořepka Street became a sanctuary for all those who knew and loved Old Prague.

The changes that were brought about by the rapid modernization of the city at the turn of the 20th century created widespread public interest in Old Prague. The Brown brothers organized protests against the planned reconstruction of Josefov and the Club for Old Prague was established soon later. It was around this time that Kohn, without any particular technical experience, set about painting his small pictures of the streets, houses and squares of the Jewish Town in an attempt to preserve their form and, in so doing, to prevent them from falling into oblivion. Apparently, he went round houses, shops and restaurants peddling his pictures for any price he could get. He hardly ever dated his works, but he often jotted down the name of the street or house on the back . As some of his pictures depict horse-drawn trams and gas lamps, it is clear that the earliest works were made before 1900. These paintings appear to have been executed with more skill and care than his later works. He continued in his artistic endeavours and, with the help of old photographs and postcards, produced hundreds of paintings of the Prague ghetto. The most valuable ones, of course, are those that depict places which are no longer to be found anywhere else and which were made during the course of the reconstruction of the ghetto.

In contrast to the work of professional artists from the end of the 19th century, who were inspired by the mysterious and somewhat gloomy atmosphere of the former ghetto, Kohn’s pictures provide a completely different view of the Jewish Town. Details of houses – windows, shop-signs, pantile roofs, dormers – goods unloaded in front of shops and street pavements were all meticulously presented in clear compositions and light pastel colours. The unmistakable atmosphere of the Jewish Town is captured in pictures of shady areas in deserted streets with narrow strips of blue sky hovering above the roofs and reflected in the top windows of houses. The unusual lighting and piercing shadows on the facades of houses in empty streets create a feeling of unsettling timelessness and nostalgia. Kohn’s work was also marked by an apparent naivety in the depiction of figurative motifs. Whenever figures appear in his street scenes, they are caught in a motionless and unnatural state, which is perhaps why they all convey the impression of loneliness.

Kohn focused almost exclusively on motifs from the Prague ghetto, creating many variations on the most prominent images – the Old-New Synagogue and the Old Jewish Cemetery. His subjects often complement and follow on from each other; when seen together from various angles and perspectives, they form a panorama of picturesque nooks and corners. Josefovská Street (now Široká) – with the New Synagogue, numerous shops and the house of Rabbi Loew – was once the main area of the Jewish Town and a dividing line between the south and north parts. The most scenic spot in the south part was Maiselova Lane, which formed the rectangular Three Wells Square at the intersection of the streets Kostečná and Jáchymova. In the Old Jewish Cemetery, Kohn mostly painted groups of tombstones around the grave of the mayor of the Jewish Town, Mordecai Maisl (1526–1601). Not far from here, in Rabínská Street, he would often depict the picturesque view of Jewish butcher shops in the shadow of the Great Court Synagogue. He also painted in the peripheral streets of Platnéřská, Kaprova and Dlouhá, which did not become part of the extended district of the Jewish Town until 1812. Individual paintings were also made in the Na Františku area, near the Ungelt courtyard, in the Old Town Square and in Na Příkopě Street. His paintings, which were almost exclusively dedicated to the former Prague ghetto still appear from time to time in antique shops in Prague.

The bulk of the reconstruction of Josefov and the adjoining parts of the Old Town – as demarcated by Platnéřská Street, the Old Town Square and Dlouhá Street – was carried out between 1896 and 1914. At around this time, a new house was built at Haštalská Street 14/752, where Kohn lived from March 1915 until the end of his life. Shortly before moving, he had apparently became involved with Anna Karasová (1891-1981), who gave birth to his daughter Markéta in October 1915. They did not marry, however, until 1918, when they had another daughter, Valérie; the youngest daughter, Věra, was born five years later. At the start of World War II, Markéta was arrested by the Gestapo, incarcerated in the Small Fortress at Terezín and deported to Auschwitz, where she died. In September 1942, the other two daughters were deported to the Terezín ghetto, where they remained until liberation. Their father was saved from deportation by his mixed marriage and by his hospitalization in 1944 in the Jewish hospital in Lublaňská Street in the Vršovice district of Prague. In March 1948 he celebrated his eightieth birthday with his family and a commemorative article about his work was published in the Prague Jewish Community Bulletin. He died in Prague on 3 April 1953 at the age of 85. He was buried in the Russian Cemetery in the Olšany district of Prague.